The Scuba Gear List Archives: Scuba Gear and Diving Equipment

What is "THE LIST" you ask? Each week, our staff of Certified Professional Instructors put together special offers, package deals, exclusive "List Member Only" discounts along with valuable and fun topics. ("THE LIST" is delivered weekly right to your in-box!) "THE LIST" topics cover a wide range of information geared to both beginners and experienced divers alike. Many of the ideas expressed are taken directly from field experience and the frequently asked questions our professionals receive. Here at Island Scuba Corporation, we believe a Certification Card is a license to learn. That is why we have organized this compilation of our past issues. We hope you enjoy browsing through our site and thank you for stopping by! Pages are updated frequently so stop back for more great gear and information.

The topics expressed are for general information purposes only and may not apply because of individual needs, skill level, logistics of the dive, various diving equipment and/or diving conditions. Always follow safe diving practices and dive within the limits of your training and abilities.

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ATTITUDE!
When neutrally buoyant while diving what position do you and your equipment rest in? In-water attitude is determined by many factors. Have you added a new piece of equipment and noticed a change? How high or low is your cylinder positioned? ATTITUDE takes continued practice and even slight changes in the positioning of existing equipment can make a difference. Spend a dive working with a buddy and find out what works best for you! Make it a habit at the beginning of each dive season, vacation or any time you add a new piece of equipment. Even a small dive light and how it is attached can make a difference in your in-water attitude. A bad attitude can ruin a dive! The time you spend will better ensure your comfort and enjoyment for future dives to come.

OUT-OF-BREATH
As certified diver's, clearing your regulator is a long since conquered skill. Many of us prefer to simply exhale, others like to use the purge button and many use a combination of both throughout their dive. Did you know there is third way to clear the regulator that works in almost any situation? Unlike exhaling, which demands you have air to expel, or purging which assumes you have access to the purge button (and it is functioning), "displacement" is a third method that you should add to your skill set. (It is also a part of many basic open water certification programs.)

As with any diving skill or technique, always practice in shallow water with a competent diving partner under controlled conditions, ideally a pool.

SKILL DESCRIPTION:

1 - Kneel on the bottom and remove your primary second stage from your mouth using your right hand.

2 - Continue to allow air to escape (exhale) while the second stage is out of your mouth. (Remember to turn the mouthpiece downward in case of any free flow from the second stage.)

3 - Replace the second stage in your mouth, work your jaw to form a suction and start to draw water into your mouth. Work your jaw again in the opposite manner to force the water out of the exhaust ports. (This technique can be compared to a game we all used to play as children with a glass of milk and a straw. Remember how you would start to draw water up into the straw and before the milk reached your mouth forcefully expel it to blow bubbles, usually to the frustration of adults around you. Displacement involves essentially the same technique.

Mastering of this skill is especially valuable in a sharing air (emergency out of air) situation. Often the diver passing the Safe Second stage has their hand covering the purge valve while the "diver in need" has fully exhaled. This is also a must have skill for any dive that involves a gas switch/change to another regulator. This skill may prove a bit difficult at first. Most divers new to this skill have more trouble with the idea of fully exhaling first than the actual exercise. Practice makes perfect!

SLIP SLIDING AWAY
Wet what? He blurted out as he put on his gear. Though commonplace to most, wetting the cylinder band before it is tightened on the tank is an often forgotten diving practice. Simply put, the nylon webbing expands once it is wet, usually causing the cylinder (tank) to slip or even completely slide out. Those "perfect" hose lengths are a bit short when the cylinder is hitting the back of the diver's calves. AND don't think an experienced diver can't forget... many a "pro" has omitted the required dunk because "they usually dive doubles".

THE FIRST RULE OF SCUBA: BREATHE CONTINUOUSLY
This is the first installment in a series of primary diving practices. While this may initially be a simple review, the concepts and ideas expressed should bring attention to although basic, often forgotten or ignored diving practices.

Have you noticed those "bubbleless" divers on TV or a buddy who never seems to breathe? While it may seem "scuba cool", they may be taking an unnecessary risk by breaking the most fundamental rule of diving.

Over expansion is a serious problem to consider when a diver is using an improper breathing pattern. What would happen if an untrained (poorly trained) scuba diver ascended from depth without exhaling? Applying Boyle's Law, the result would be an over expansion of the diver's lungs potentially resulting in serious injury. While the concept of a diver holding their breath and fully ascending to the surface may seem a bit extreme for experienced divers, an injury of this type could occur by the diver ascending as little as 4 feet without exhaling.

Breathing Continuously, simply put means that you are always breathing, in or out while on Scuba. If the mouthpiece is out of your mouth for some reason, then you should be exhaling a small stream of bubbles. Do not hold your breath. In an emergency situation, a diver will react with learned habits: good, bad or otherwise. A proper breathing pattern will make each and every dive safer and more enjoyable.

THE SECOND RULE OF SCUBA: ASCEND SLOWLY AND MAINTAIN CONTROL
Both new and experienced recreational divers may take for granted the easily executed ascent phase of the dive. Though seemingly simple, it is often during a transition phase of a dive (such as beginning an ascent) that unnecessary complications and risks occur.

Last weeks issue gave an over view of one of the primary effects of pressure on ascent in relation to the first rule of scuba. In further combination with this topic, a diver must never loose control while ascending to the surface. A well-executed dive plan utilizes the ascent phase of the dive to increase the overall safety of the buddy team and better prepare for conditions encountered on the surface. By performing a proper ascent procedure, maintaining a proper ascent rate and executing a safety stop in accordance with the no decompression dive plan each and every dive will end as well as it began.

A proper ascent should never exceed an ascent rate of 30 feet per minute or 1 foot every 2 seconds. A diver can accurately monitor their ascent rate by using a properly functioning depth gauge and timing device. Also, many dive computers include ascent rate indicators, which alert the diver to unsafe ascent rates. Through practice and by careful monitoring, proper ascent rates can become almost automatic.

THE THIRD RULE OF SCUBA: ALWAYS MAINTAIN NEUTRAL BUOYANCY AT DEPTH
A "safe" diver integrates proper diving practices at each and every phase of the dive. Preparation and proper execution directly impact the overall safety of the entire dive profile. To increase your safety while diving it is vital to follow the Third Rule of Scuba: "Always maintain neutral buoyancy at depth".

In addition to affecting the overall enjoyment of a dive, possible in-water "emergencies" will be better dealt with. Practically, when a diver fails to achieve neutral buoyancy, swimming becomes more difficult and tiring. Gas (air) consumption increases and fatigue is more likely. Swimming speed is decreased by a causal increase in drag making the dive "work" instead of fun. If a dive plan is improperly executed (or the plan was flawed/incorrectly planned) a diver finding themselves in a emergency situation will be better prepared to react if they are neutrally buoyant. Because the air in the BC will expand on ascent, only minimal effort is required to achieve positive lift. Further, by venting air from the BC during an ascent a diver or buddy team can perform a controlled emergency ascent. Remember, always plan your dives and dive your plan!

THE "3 R" RULE
While discussed in detail during the classroom sessions of many basic diver training programs, most divers never "practice" the proper response to difficult situations. Ideally, the best way to deal with a problem is to never have one. However, a properly trained diver can respond to difficult situations underwater and render them workable. The defined decision matrix of the "3 R" Rule is as follows:

TELL ME WHAT'S ON YOUR MIND "BUDDY"!
Being an effective member of the buddy team includes communicating with the each other throughout out the dive. Though it is always nice to bring a hiding Sea Turtle to attention, proper communication includes agreeing to move to each transition phase of the dive. Effective communication will maintain the integrity of the buddy team, reduce stress and increase both members overall enjoyment of the dive.

In application: as the buddy team moves from the surface phase of the dive to the descent phase of the dive it is vital that both members first agree to begin the descent and then maintain communication for unplanned pauses. As an example, divers should not become separated because one team member had to clear their ears or adjust equipment. After reaching the bottom the team should again pause to effectively agree on direction before swimming off to the bottom phase of the dive and on so on. These deliberate preparations to move into each phase will benefit both team members before, during and after the dive. There may be a reason why that last buddy is not returning phone calls...

SAFE SECOND OR SECONDARY SAFETY?
Diving with an Octopus, also known as a Safe Second is standard practice for most divers and part of basic diving procedures. As you may be aware, your "buddies" Safety Second Stage is for you and vice versa. Dragging the mouthpiece through the sand probably is not much of a problem for the donor diver and rather a significant issue for the recipient. Each buddy team member should take responsibility for the availability, function and securing of the corresponding safety second stages. Proper performance, hose length and orientation are also reasonable expectations for each member of the buddy team to have. A few simple adjustments and a proper Safe Second Retainer (securing device) can truly make the difference. Never allow your safety to become secondary, even if it means choosing another diving partner.

Of course the best way to deal with an emergency is to never have one... Proper dive planning and practices are always mandatory.

REDUNDANT BREATHING SYSTEMS (RBS) & SLING BOTTLES
The concept of more than one cylinder, though most commonly associated with "Technical Diving" also has significant application to the recreational diver when he or she chooses utilize the benefits of a Redundant Breathing System (also known as a "Pony System").

Diving statistics from many sources all closely agree that 50% of diving fatalities and 70% of accidents overall, occur from out of gas (air) emergencies. Utilizing an RBS eliminates the need to share air with a buddy or perform an emergency ascent to the surface. By incorporating a totally independent breathing system into the total diving system a diver can avoid "out of air"/"loss of air" emergencies. As with any and all diving equipment proper training and equipment configuration are a must. While the latest "basic open water" diver programs now incorporate the use of an "RBS", a diver will need to practice in a controlled environment before "jumping in".

An RBS is comprised of a small high pressure cylinder, standard valve, regulator first stage, a second stage with a low pressure hose of 36" to 39", a mounting device for securing the system to the main cylinder and an optional cylinder pressure monitor.

Divers may wear the RBS on either the left or right side of the main cylinder. The choice of configuration is not arbitrary and depends on the make up of the main system.

A RBS while similar in components is very different in application than a "sling bottle" or "stage bottle". Keep in mind, many divers use theses terms interchangeable. In general, a sling bottle is worn on the front of a divers body. Yes, this may seem awkward above water but when rigged properly the cylinder hangs in line with the divers body while in a swimming attitude. Sling bottles like stage bottles, do not apply for "recreational" profiles. Stage bottles are not worn during the dive and rather positioned at points of the dive. As an example, a diver may securely position a "deco" mix on/by the ascent line to use during the ascent phase of the dive. Stage and sling bottles are often a different "mix" than what the diver is carrying with them and utilized to meet the gas and profile requirements of Technical/Extended Range/Tri-Mix dives. Here are some common application tips preferred by many recreational and technical divers alike for their redundant systems.

VALVE RING: Many divers have a brass ring installed at they cylinder neck. (The valve needs to be professionally taken off and reinstalled to do this). It provides an added place to attach clips and secure the second stage or hoses.

ADJUSTABLE SECOND STAGE: An adjustable second stage allows the regulator to be "tuned down" when it is out of the divers mouth therefore considerably less likely to free flow. The diver can readjust the second stage for easy breathing during use.

COVER YOUR CLAMPS: When using clamps the leftover tail should be covered and trimmed. The metal tail can hook and snag on equipment, lines, etc. Some divers completely cover the clamp with a tubular type of nylon webbing and tuck the leftover tail into it.

DUCT TAPE RULE: While the wonders of duct tape continue to amaze us all, it is not considered an appropriate mounting device. Avoid dive buddies with visible duct tape usage.

SECURE YOUR HOSES: Dangling gauges and second stages are always to be prevented. Equipment must be secured properly so it can be quickly deployed when needed. Unsecured hoses damage the reef/environment or the reef may damage them.

"HANDY" SIGNAL REVIEW
Before embarking on any dive it is vital that the primary hand signals (and any other profile specific) be reviewed and agreed upon. Being able to effectively communicate during the dive will make for a safer and more pleasant experience.

There are set standards for each hand signals. Always use the same signals so that a high level of communication will already be established.

Before each dive and/or with each new diving buddy, both should review:

CAN YOU FLY?
Here is a great neutral buoyancy test called the "FIN PIVOT". It is a great dive warm-up and is exceptionally valuable when new equipment has been added and/or configuration changes have been made to the diving system.

SKILL DESCRIPTION OVERVIEW:

From the kneeling position shift forward to a prone position. Feel the change in buoyancy; inhale vs. exhale. Slowly add air to the BC. Gently, add small amounts on the inhalation cycle or only once per cycle until your torso lifts off the bottom. Fully extend legs while continuing to add air until your body pivots on the fin tips. Neutral Buoyancy is a learned skill that requires some practice. When properly performed, by shortening the depth of the inhale and exhale, a lesser shift in buoyancy results. Further more, by increasing the depth of the inhale and exhale a greater shift in buoyancy results.

PRIMARY RECOVERY
An effective skill used by divers on almost every dive redefined...

Recovery of the Primary 2nd stage Skill Description:

To locate the primary regulator should it not be hanging over your right shoulder: Drop your right shoulder while leaning forward. Extend your right arm down your right side, maintaining contact with your body. Sweep your arm back behind you and then return your arm to the front of your body. The hose will now be in the front of your body, usually near the bend of your elbow.

If the hose is snagged on the valve or another hose, you may need to locate the hose at its point of origin; the regulator first stage. Using your left hand reach under the cylinder and raise it up while reaching over your shoulder with your right hand. Locate the hose and encircle it with thumb and forefinger running your right hand down the hose to locate the Primary 2nd stage. Remember, your safe second (octopus) is another viable alternative should recovery become necessary in an at-depth situation.

As with any diving skill or technique, always practice in shallow water with a competent diving partner under controlled conditions, ideally a pool.

YOUR BC AND YOU AFTER THE DIVE
The dive is over, the boat has docked and your gear is patiently waiting for your attention. Before running off to work on a tan, spend some "quality time" properly rinsing your equipment and getting it ready for the next dive. The few moments spent will keep your gear in proper working condition for next time.

Before rinsing remove any accessory equipment attached for the dive. Keeping them attached may cause unnecessary added wear or weaken the attachment point. Rinse them separately according to their care needs.

Start off by draining any excess water from the bladder. The easiest way to do this is to fill the BC about half full with air, and drain the water out by holding the oral inflation valve at the lowest point possible (keeping the inflator hose straight) and pressing the oral inflation button.

After all the excess water is out, rinse the inside of the BC by first again, inflating the BC half full. Add clean fresh water through the oral inflation mouthpiece. Fully inflate the BC and swish water around to completely rise the inside. Then drain the water completely.

Thoroughly rinse the outside of the BC with fresh water. A soft toothbrush is a great tool for removing sand from the Velcro. Pay extra attention to the inflator and quick disconnect fitting. If necessary use the toothbrush to remove visible sand and debris.

Make sure the BC is partially inflated during storage and keep in a cool dry place. Follow the manufacturers recommended service intervals. If you are a frequent diver your BC may need to be serviced more than once a year.

2 AND 2 OR 3 AND 1?
Two and two is a common term for the hose configuration of a standard recreational scuba regulator system. Specifically the right side (or the 2 hoses coming over the divers right shoulder) are where the primary diving regulator and the secondary regulator (often referred to as the octopus) are ported. The left side is where the power inflator and instrumentation (high pressure hose) hose are configured.

Three and one is another configuration that has also been taught for many years. Specifically, the primary alone is ported on the right side while the power inflator, high pressure hose and secondary regulator come off the left side. The major benefit of this configuration is, it now changes the positioning of the secondary regulator (safe second), making it "right side up" for the diving buddy or diver in need.

Conventional diving second stages have a right side up and upside down. When a conventional second stage is upside down, the regulator will breathe very wet. It will also require the diver to tilt their head forward as far as possible in order to get a clear breath. If a diver in an out of air emergency was passed an upside down second stage, they would not likely have the piece of mind to address the added complication. This is especially important to consider because some basic diving courses do not teach upside down regulator clearing. Because of these factors many divers are re-rigging their systems with a 3 and 1 configuration. Another benefit is that by only having one hose of the right side, recovering the primary second stage is easily accomplished. (Covered in a separate topic.)

Did you know? The 2 and 2 configuration is a throwback from early diving first stage designs. (Remember open circuit recreational scuba diving is a relatively new sport.) Early diving first stages had very few ports for hoses, and most divers did not use BCDs. As the use of a safety second (and BCDs for that matter) started to catch on there was usually only one open port on the right available. Though many advancements have been made, and ample ports became available the practice still continues.

Set up your equipment with your buddy and see how you both are configured. Run through the different options and see what works best for you. Buddy teams should also have the same configurations to increase safety. If you are considering any changes, evaluate them in a controlled environment (ideally a pool). Practice emergency procedures and in-water skills before putting them to the test on an open water dive.

SPARE WHAT??
There is always an ongoing debate about what a spares kit should include. Specifically, what items are a must and what is just an attempt to fill your gear bag with useless stuff.

A proper spares kit should include equipment specific items for your scuba system and the types of diving you do. If you never dive with a light, your spares kit should obviously not include a spare bulb. In contrast, if your diving (like wreck diving and night diving) requires you to dive with a light or two all the time, your spares kit should include at the minimum spare bulbs and o-rings for the lights you dive with.

Here is a brief descriptive list of what you may want to include:

Mask Strap: an inexpensive mask strap can be a real dive saver. Make sure the strap actually fits your mask, as not all mask clips fit the same size and thickness strap.

Spare Mask: a mask that fits is worth its weight in gold. Keep a spare mask with your kit for those on site emergencies. A low volume style will transport well and is not likely to break. (Keep it in a protective mask box just in case)

Snorkel Keeper: an "old style" figure 8 snorkel retainer can save a dive every time. Better to have a few of these. They can be used quite creatively as a safe second (octopus) retainer, console holder and more in a pinch.

Tie-Wraps: hundreds of uses for these little guys. Not only can they be used to affix a scuba mouthpiece, they can reattach a broken clip in a bind. Some tie wraps are made out of material (generally, the white kind) that makes them very susceptible to UV rays. With exposure, they can become brittle and useless.

O-rings: keep a few to fit your equipment and the cylinder valve faces. If you use a DIN fitting on your regulator also have a bunch to fit. If your system is set up for Nitrox, you should have Nitrox compatible o-rings. It is also a good idea to have some o-ring lubricant. There are different grades for breathing systems and general use (like camera or light o-rings) so make sure you have the correct type(s). Nitrox, systems also use a different type of specifically oxygen compatible lubricant.

Spare Clips & Snaps: rigging accessories seem to have legs of their own so always have extra in case you need to make an on site replacement. Include comparable types to what you dive with, so there will be no "transition" if you need to make a switch.

Fin Buckles and Straps: another must have item that requires a little extra attention. There are very few "universal" fin straps because there are so many different models of fins and clips. Again, make sure the strap actually fits easily. Have a spare fin buckle (or two or three). Fin buckles are subjected to much abuse in additional to normal use. Again make sure they fit your fins, some that "look like they will fit" may not work at all.

Mask Defogger and Slate Cleaner: Have an extra bottle of de-fog in you spares kit in case you run out or the one in your dive bag "gets borrowed". Remember to prep the surface of the mask with mask cleaner (also called slate cleaner) before the first use. Masks have a film from the manufacturing process on the lenses when they are new that will prevent de-fogger from working. It doubles as a great cleaner for dive slates. (Always start you dive with a "clean slate"!)

Tools: A pair of quality adjustable wrenches, pliers and a small screwdriver or two can make or break a dive. Spend a little more on quality here as salt water will quickly destroy lower quality tools. A universal scuba tool is always a good addition because it has most of the sizes needed for scuba, including the Allen keys.

How you choose to transport and store your spares kit is also of vital importance. Hard, o-ring sealed boxes are popular choices. Keep in mind any moisture that gets into the box (like if your hands were wet when you took an item out) can cause corrosion and damage to the items inside. The o-ring seal will not let the moisture evaporate and in the case of salt water especially, make quite a mess. Most tools will rust if kept in a wet sealed box, so remember to include care and restocking of your spares kit in your post dive regimen. Rinsing and lubrication is also an important part of maintaining your spares kit.

STUFF IT!
Transporting and storing your scuba equipment system is an integral part of the dive itself. Proper packing will avoid damage to equipment and ease gearing up.

When getting ready for the dive day, lay out the entire scuba system. Position items in relation to where they will be worn. Lay your suit on the floor and position your gloves at the wrists and your boots at the ankles of the suit. If you use a wrist mount computer or gauge, lay that in position where you will be wearing it in the water. Mask and snorkel at the top of the layout, fins by the boots, and so on. Build the layers of equipment the way you will wear them in the water. By using this type of layout you can eliminate leaving something behind. The diver is able to overview the entire scuba system at a glance. This works best (and is more fun) when done with a buddy. If there are any differences in rigging configuration, they will be immediately brought to light. The final packing phase will also be more efficient and take less time.

Pack your equipment bag in the reverse order that you will use the items. Keep in mind to group like items together. As an example, your mask should be near your snorkel (ideally in the same pocket) your boots with your fins etc...

The last item you will put on should be the first item in the bag. Separate pockets are a must have for scuba divers. Not having them can practically impact getting geared up. If your bag does not have many pockets, use smaller bags to consolidate items. In general, a diver will likely set up their BC before they put on their wetsuit, therefore the BC should be packed on top of the suit as it will come out first. DO NOT confuse pre-dive preparation for transport and gear up with proper storage. Wet suits and BCs as an example should be stored hanging up on a proper hanger that will not damage the equipment. Only after a complete rinsing and drying of course!

Whenever possible use a protective case or box for your mask, regulator, computer and other more sensitive equipment items. Did you know that a diving computer or gauge face can become scratched in your equipment bag if care is not taken?

Keep small items together in a small mesh bag or protective storage box. Small items can easily roll over board or get dropped in the sand never to be seen again. Keeping them together will also make them easier to find and use.

If you are a vacationing diver, you will likely use a large, heavy weight bag for the airplane. Once you arrive at the dive site, try keeping the essentials in a good size mesh carry bag. (Leave the main bag in the room). Many dive operations provide hooks or a locker near the beach and boats for the duration of your stay. If you are bringing your full size bag onto a boat, keep all the zippers closed. Should someone get seasick your gear will remain safe (and dry). It is also a good idea to keep your regulator separate as a carry on, and during transport. Some bags have a pocket specially sized for the regulator when in its carry bag. Once you arrive, you are back to one main bag.

Last but not least, cylinders should be carried separate. Your dive bag will thank you. It is also important that you do not transport the system with the regulator attached to the cylinder. It can cause permanent damage to the cylinder valve and regulator first stage.

DO THE MATH
When determining how much ballast (weight) a diver should use it is important to consider the type of cylinder (tank) being used during the dive. Many divers find themselves weighted "just right" at the beginning of the dive only to become positive half way through. This occurs because of what the compressed air in the cylinder actually weighs. As the diver's PSI drops, the cylinder becomes lighter.

Air weighs .08 per cubic foot. When compressed into a scuba cylinder this becomes a significant factor to take into consideration. As an example, if a cylinder holds 100 cubic feet of air, the air itself weighs 8 pounds. When the cylinder is half full the air will weight half as much, 4 pounds. When the actual buoyancy characteristics of the cylinder are added into the equation a diver can accurately determine how much weight he or she will need to compensate.

An aluminum 80, one of the most popular size cylinders in use today holds 80 cubic feet of air. The compressed air weighs 6.4 pounds. The cylinder itself (buoyancy characteristics) weighs +4.1 pounds in the water when empty. Basically the cylinder floats. When completely full, the cylinder is -2.3 pounds in the water. In other words, the weight of the air causes the cylinder to become negatively buoyant by 2.3 pounds. As the diver uses the air in the cylinder it become less and less negatively buoyant. At 1500 PSI the cylinder is positively buoyant by about 1 pound. At 500 hundred PSI the cylinder is positively buoyant by about 3 pounds. Consider the importance of performing a controlled ascent with a safety stop at the end of a dive. Envision how an improperly weighted diver could be affected. The diver must carry ballast to compensate for the requirements and changes of the total diving system.

Another common cylinder is a High Pressure Steel 100. This cylinder is neutral in the water when empty. When full, the cylinder is 8 pounds negatively buoyant in the water. This is important for a diver to consider, because there is easily a 4 pound (or more) shift in buoyancy. A diver should be properly weighted for the end of the dive. A properly functioning, high quality BCD, with ample lift capacity will easily compensate for these fluctuations when used effectively.

Below is a general (exacts vary from one manufacturer to another) listing of cylinder types with their characteristics:

Cylinder Type: PSI/Cubic Feet/Weight Empty (lbs)/Buoyancy Empty (lbs)

TO BE OR NOT TO BE NITROX
With the ongoing in advances in technology, NITROX also called Enriched Air, EANx, SafeAir (tm), and several other names has become increasingly popular. One of the most common misconceptions is that Nitrox is only for deep and technical diving. Well, this couldn't be farther from the truth. While mixtures other than air are used by deep and technical divers, enriched air mixtures provide the greatest benefits between 40 and 130 feet. Every recreational diver, even the occasional diver can benefit from the reduced nitrogen levels of Enriched Air.

Enriched Air is simply air that is enriched with additional oxygen. Generally the mixture has an oxygen concentration between 22% and 50%. Because of the requirements a proper blending station must maintain to ensure safe practices, Enriched Air is cleaner than ordinary compressed air because it contains less condensed hydrocarbons. It is NOT a "mixed gas", used only by commercial and professional divers. Enriched Air and can be used by any properly trained recreational diver.

Although no special diving equipment is required. The diver's cylinders and regulator system must be properly cleaned and serviced for Enriched Air mixtures according to manufacturer's guidelines. While there are still some underground debates about the necessity for cleaning and converting equipment, it is the safest practice. Many manufactures make "Nitrox Ready" equipment right out of the box.

The reason for conversion (and or cleaning) is that some of the parts and lubricants used in diving equipment are not compatible with higher percentages (than air = 21%) of oxygen. These incompatible materials contain hydrocarbons which when combined in an oxygen rich environment under pressure can cause, flashing (incomplete combustion) or an explosion. One of the most serious possibilities of flashing is that it will cause Carbon Monoxide to be produced. You may remember from your classes that Breathing Carbon Monoxide is dangerous and can even cause death. Proper gas blending procedures, using the required grade of air (a higher standard than the minimum "air" standard) combined with proper equipment avoids these issues.

The major advantages of diving with Enriched Air instead of air are increased safety and protection from decompression sickness. Specifically: No decompression time limits (NDL) are significantly extended which adds an extra safety margin and/or increases allowable bottom times. Decompression time is reduced (if NDLs are exceeded). There is a reduction of nitrogen's narcotic effect and post-dive fatigue levels. After a dive, residual nitrogen in the body is reduced which increases the available bottom time on repetitive dives, decreases surface intervals, or both. This also reduces the risk of flying after diving. With an Enriched Air mixture you are breathing less nitrogen. Nitrogen is the major limiting factor for recreational dive profiles.

Enriched Air diving requires certification in addition to a basic certification. There are also more advanced levels for decompression and technical profiles. Because no new in-water skills are required for the basic Enriched Air Certifications (breathe in / breathe out) the additional dive planning skills can be easily learned in a classroom setting. The classes usually last 4-8 hours depending on agency and level. A dive or 2 is also required and it will be the most fun" certification" dive you will ever do. As always, be safe, ask questions and use a safe total diving system.

IT'S THE PRINCIPAL
As scuba divers, proper buoyancy control is necessary for safe and enjoyable dive experiences. The function of buoyancy is based on Archimedes' Principle: Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.

We already understand that a negatively buoyant object will sink, a positively buoyant object will float and a neutrally buoyant object will neither float of sink. Hence part of all the fun. The reason why an object (or diver in this case) has a specific buoyancy characteristic is based on not only its weight, but also the amount of water it displaces. A very heavy Cruise Ship floats because displaces a large amount of water.

While Archimedes' principle works for any fluid, we as divers are mainly concerned with fresh and salt water. Equal volumes of fresh water and salt water do not weigh the same because of the extra dissolved minerals in salt water. Specifically, a cubic foot of fresh water weighs approximately 62.4 pounds and a cubic foot of salt water weighs approximately 64 pounds.

If you place a box, 1 cubic foot in size, that weighs 63 lbs into fresh water, the object will displace 62.4 lbs of water. This box will be negatively buoyant. Though it is being buoyed up by a force equal to 62.4 pounds, it weighs 63 pounds. Thus, in the water it will weigh .6 pounds.

If we put the same box into salt water, it would be buoyed up by a force equal to 64 pounds (remember it is displacing 1 cubic foot). The same box would be positively buoyant in salt water by one pound. If we wanted to make it neutral we would have to add one pound of weight without changing the amount of water being displaced. The box would now weigh 64 lbs, and be buoyed up by a force of 64, thus being neutrally buoyant.

Putting the theory into practice, divers use ballast (weight) to compensate for the amount of water they displace in relation to the total weight of a diver in a scuba system. As an example, let's take a diver who weighs 150 pounds and add the weight of the scuba system to determine total weight. In this case the system weighs 58 pounds before ballast is added. The total weight is 208 pounds (150+58). Now if we could submerse the diver in a full tank of water, measuring the amount of water that overflows when he gets in, we could find that this diver displaces 3.5 cubic feet of salt water. By multiplying 3.5 by 64, we would find that the diver is being buoyed up by a force of 224 pounds. Keeping in mind that the total weight of the diver is 208 pounds. We can now determine that the diver the will be positively buoyant by about 16 pounds. In order to sink, this diver will need to add about 17 pounds of ballast. Some divers may prefer an extra pound or so and compensate with their BCDs.

Elaborating on this a bit further, take the same diver on a fresh water dive. In fresh water this diver will be buoyed up by a force equal to 218.4 pounds. Remember fresh water is slightly less dense than salt water. 3.5 cubic feet of fresh water weighs approximately 218.4 pounds. This same diver would need about 12 pounds of ballast to sink in fresh water if all other factors remained the same. As divers we determine how much ballast we should use by experience, trial and error, but the physics still apply. Consider this when making weighting decisions and modifications.

A BRIEF HISTORY
The Open Circuit Downstream Demand "SCUBA" Regulator in common use today is actually considered a relatively modern invention. Closed Circuit Rebreatheres (which are now gaining mainstream attention and popularity in the technical diving community) were invented over 170 years before. As Scuba Divers we must use our air as efficiently as possible because we only have one opportunity. With each exhalation we literally "exhaust" our air supply. The idea of recycling the air is a sound one and modern technology has caught up with the innovative concept. Below is a brief history of some of the major diving inventions with their corresponding inventions "according to the history books"

Divers probably began using snorkels made of hollow reeds about 100 A.D. as the first piece of diving equipment. By 1300, Persian divers were using underwater eye-goggles, made from the polished shells or tortoises. In the 16th century, barrels were used as primitive diving bells, and for the first time divers could travel underwater with more than one breath of air, but not much more than one.

In 1771, British engineer, John Smeaton invented the air pump. A hose was connected between the air pump and the diving 'barrel', allowing for air to be pumped to the diver. In 1772, Frenchmen, Sieur Freminet invented a 'rebreathing' device that recycled the exhaled air from inside of the barrel, this was the first self-contained air device. Freminet's invention was a poor one, the inventor died from lack of oxygen after being in his own device for twenty minutes.

In 1825, English inventor, William James designed another self-contained breather -- a cylindrical iron "belt" attached to a copper helmet. The belt held about 450psi of air, enough for a seven-minute dive.

In 1876, Englishmen, Henry Fleuss invented a closed-circuit, oxygen rebreather. His invention was originally intended to be used in a repair of an iron door of a flooded ship's chamber. Fleuss then decided to use his invention for a thirty foot deep, dive underwater. He died from oxygen toxicity because he well exceeded the maximum operational limits for pure oxygen. (Remember modern divers use air (about 21% oxygen 79%) nitrogen and Enriched Air, also called Nitrox which has an oxygen content between 23% and 50%. Enriched Air Mixtures with an Oxygen content of 32% are one of the most popular in use.

In 1926, French naval officer, Yves Leprieur invented a system using a 2,000-psi steel tank, which flowed air into a full-face mask.

In 1939, American, Dr. Christian Lambertsen designed a 'Self-Contained Underwater Oxygen Breathing Apparatus' for the U.S. military. It was part of the war effort, code-named 'SCUBA'. Lambertsen's 'SCUBA' gear worked for shallow dives, but the gas mixture was wrong for greater depths and divers were dying from the oxygen toxicity.

In 1943, Frenchmen, Emile Gagnan and Jacques Cousteau invented the demand regulator, which adjusted the air pressure automatically, supplying air as the diver needed it. Gagnan had started design work on a similar regulator for automobile research, when cooking oil was used to replace gasoline during the war. Gagnan designed a new regulator to work with the cooking oil fuel. Together, Gagnan and Cousteau further improved the designs of diving equipment. Their regulator was connected to three cylinders, each holding 2,500 psi of air. The complete equipment, or autonomous diving suit with the pressure regulator, was called the "Aqua-lung". The "Aqua-lung" is the basis for modern equipment used today, most historians refer to Gagnan and Cousteau as the fathers of modern scuba diving gear.

BREATHE IT AGAIN SAM
Open circuit scuba is the mainstream system of choice for recreational divers. Over the past few years major innovations in technology combined with lower production costs have changed the standard for a well equipped diver. BCs with power inflators, diving computers, and integrated weight systems (just to mention a few) have long since become the norm for the average diver today.

Once again, revolutionary changes are taking place as "Rebreathers" make their way into the main stream market (and rightfully so). Rebreathers also referred to as closed circuit systems, have considerable advantages over open circuit scuba. These main advantages are:

1. 30-50 times greater gas utilization efficiency! Permits hours of bottom time with only 15-30 cu. ft. of breathing gas consumed.

2. Substantially smaller, lighter load increases freedom of movement. Diving becomes easier and less stressful for smaller divers and reduces the cylinder loading for long duration dives.

3. Re-breathing the same warmed gas conserves divers body temperature to increase diver comfort and permit longer dives in colder environments.

4. Recirculation of respiratory moisture reduces diver dehydration, a prime pre-disposition factor to DCI.

5. Elimination of exhaust bubbles and noise allows closer contact with sea life.

6. On-board computerized, constant real-time gas blending permits the optimum breathing gas blend at all depths. Decompression obligations are greatly reduced.

For many people, open circuit scuba will continue to meet the needs for their diving objectives. Divers will make their own evaluation of the safety advantages inherent in the new rebreather technology. As time passes and production volumes increase, costs will decline and more and more divers will experience "silent scuba". Basic entry level training programs taught exclusively with closed circuit systems are actually not as far away as they seem.

RIGGING AND YOU
Of all the different types of diving configurations and standards, accessory rigging is the most common, with the least amount of "official" do's and don'ts! Part of the reason for this is there are a lot of options combined with quite a bit of after market products. The first important point to remember is "Keep It Simple". This not only applies to the configuration or accessory attachment itself, but the type and amount of accessories used.

As a practical example, a piece of equipment is only as much of a value in proportion to the diver's ability to deploy it. While a lift bag and line reel (or Jersey Reel depending on training and philosophy) can be effective should a diver be unable to return to the anchor or ascent line, if a diver cannot use it properly they can become a life threatening hazard. The same is true for any number of "safety accessories" and accessory equipment.

Before putting it to the test, any new piece of equipment or change in rigging configuration should be tried and tested in a controlled environment. Ideally a pool. It is always a good idea to perform a dive or two with your buddy in a area that is both familiar and comparably easy to dive in before "jumping into something." If changes are needed, the buddy team will be able to evaluate them effectively while minimizing or eliminating potential risks. It will also give the team an opportunity to practice using the accessory item. Unclip and reattach, practice deployment and/or emergency procedure. Again, an item is only as good as the diver's ability to use it.

Diving lights are one of the most commonly used (and commonly lost) diving accessories. They vary in size from small penlights to advanced systems with external battery housings. When using a large light (or other large accessory), divers most commonly experience buoyancy and in-water attitude issues caused by improper trimming. In general, the scuba system has a natural forward pitch to the left. This is mostly attributed to an imbalance caused by the inflator and instrument console being located on the left side. How high or low a diver should position the light (as an example) will vary by body type and equipment being used. It can however be very beneficial to rig the light (or other single) accessory on the front right side. Many divers also find this convenient because they are right handed.

Another consideration is the type of lanyard on the light (or accessory). While wrist type lanyards are very popular, they can cause some issues which should be considered. In practice, they cause the diver to be more aware of their arms which tends to make them "scull" more. Because divers really do not use their arms for propulsion the extra sculling will increase air consumption and negatively affect overall comfort in the water. The accessory also has a greater tendency to slip off and get lost and/or get in the way. A good lanyard whether homemade or store bought should allow the diver to be hands free, with the accessory still close to the body for ideal trim.

Keeping the accessory close will also minimize damage to the reef and damage to the equipment itself. While this may seem like a simple concept make a note to observe others on your next group dive. The dragging lights, hoses and other accessories will prove very educational. In many cases these same divers will be using more lead than they need and having unnecessary buoyancy problems because of it.

The "accessory retainer" should also include a main tether that stays connected to the diver throughout the dive. That way if the accessory is accidentally dropped or comes loose it is not lost. A second clip or quick release is a good way to pick up the slack of the main tether when not in use and will allow the diver to unclip when the accessory needs to be deployed without fully disconnecting it. Smaller accessories should use a smaller version of the same system to be sure each dive is ended with the same equipment it started with. These same principals also apply to underwater cameras and other specialty items. When using combinations, it is important to balance the items for ideal trim. Weight can also be repositioned unequally in extreme circumstances to compensate in such a situation. Keep these factors in mind for whichever accessories you may use and each new piece of equipment you may add in the future. This type of awareness will often make the difference.

FUZZY SCUBA
Though more and more divers join the ranks each day as the sport continues to grow, many popular misconceptions are still proliferated. Regardless of certification, level or lack of certification these sometimes funny but potentially serious "ideas" still linger about. This week's Tech Tips outlines some of the more common ones and the facts surrounding them.

"Buy the biggest tank you can find!": Yes, it is true that the amount of air (gas) a diver carries is important, but visual size is not necessarily and indication of actual volume. As an example, a standard Luxfer Aluminum 80 has an Outer diameter of 7.25". The length (height of the cylinder) without the valve is 26.06 inches and the actual capacity (volume of gas) is 77.4 cubic feet. In comparison a Faber Steel 100 has the same outside diameter (7.25") and is about 2 inches shorter (24.01") with a volume of 100 cubic feet. Standing side by side the Luxfer 80 looks bigger but the Faber 100 actually has 22.6 more cubic feet of gas, which equals out to about 29% more.

Sharks: Keeping in mind that divers are ocean visitors and guests in their environment, sharks actually pose little hazard to divers. Divers give off different vibrations than swimmers and surfers. We are also comparably large in size and the bubbles we blow are quite scary to many forms of marine life. (Marine Biologists and Underwater researchers often have to use "bubbleless" systems to get close to marine life.) For all they hype sharks receive there are very few incidents each year. Especially when compared to increasingly high numbers of dives performed. According to the ISAF (International Shark Attack File) they investigated 65 alleged incidents of shark-human interaction occurring worldwide in 1999.

Floaters: There has been quite a bit of controversy over the past 20 years or so about how specific types of BCDs (Buoyancy Compensation Devices) float the diver on the surface. BCDs are not and never have been "life jackets". Though early BCDs had many similarities, even these units did not perform the same way by design. After many years of testing by certification, independent and subcontracted agencies no specific design will float the diver on the surface in any one orientation consistently. In fact, according to a recent quote from Rodale's Scuba Lab "No BC we have ever tested has ever been able, by itself, to consistently float a diver face up."

The 40% Myth: The issue of Oxygen cleaning and compatibility has been a "hot potato" since Enriched Air Nitrox emerged on the diving scene. The 40% Rule essentially states (depending on whom you talk to) that oxygen dedication and cleaning are not required if the oxygen content is less than 40%. Much to the contrary, outside the diving industry there is and have been very defined standards and procedures in place. It is only within the diving industry that this controversy exists. Documentation, standards and procedures from but not limited to: International industrial standards, the scuba equipment manufacturers recommendations, training agency standards, OSHA, US Navy, NASA, CGA, NFPA, ASTM and quite a few more require cleaning and dedication to be performed at much lower oxygen percentages. Many Certification Agencies and manufacturers within the diving industry do not support the 40% rule. Regardless of which camp, there is agreement that cleaning and dedication is a safer more conservative approach for Nitrox Systems (EANx). As recreational divers, safety should always be the first and foremost consideration.

CYLINDER DO'S AND DON'TS
The diving cylinder (tank) is one of the most significant parts of the diving system but is usually neglected the most. The following are some general cylinder filling, care, maintenance and important warnings. Each cylinder type and manufacture has product specific guide that may include additional warnings, care and maintenance requirements. Visual Inspections, Hydrostatic Testing and Nitrox handling standards are not scams to get the diver back into the dive shop. They are for the safety of every one that dives with or come within proximity of the tank.

SAFE SPACE
Safe Space is a little known term that essentially refers to the margin of safety built into a divers profile. It is specifically related to the actual profile when compared to the way it is charted on a dive table. Safe Space is once again gaining mainstream attention as more and more divers exclusively use dive computers.

When using basic dive tables the profile is based on the maximum depth reached for the total time of the dive. As a example: a diver performs a dive for a total time of 45 minutes and the deepest part of the five was 58 feet. On just about every recreational dive table the depth will be rounded up to the next highest, in this case 60 feet. Even if the diver only spent 2 minutes of their dive at 58 feet and the rest at 30 the entire profile charts at 60 FSW (Feet of Sea Water) on the dive table. Visualizing the way this is represented on the tables is often referred to as a "square profile". When the divers actual profile is superimposed over the square profile the "extra space" is referred to as "Safe Space". The safe space represents the inherent conservatism and additional built in safety factors to the recreational dive tables.

Diving Computers calculate a more accurate profile. They often use the same algorithms as the tables and simply perform that same calculation several times a second. Going back to the above example, the dive computer knows that only 2 minutes were spent a 58 feet. The benefit of this usually more bottom time. (Of course air consumption rates limit many divers from taking advantage of this.) A potential disadvantage is due to the fact that the "safe space" has been removed from the profile. By essentially calculating more accurately much of the built in conservatism of the diving tables is removed. This can become a significant issue when doing multiple dives over short periods of time and diving close to the edges of nitrogen limits. Keeping this in mind, procedures like performing slow ascents with proper safety stops become very important. Individual factors that predispose one diver over another (physical predispositions to DCS/DCI) should also be considered when choosing a dive profile. As with many things awareness is often the best method of prevention. Many divers use Enriched Air (Nitrox) with their air computers to add the "safe space" back into their profile. Consider your "safe space" when planning you next dive before jumping in.

ARE YOU HIGH-RISK?
While diving tables and dive computers can accurately perform the mathematical calculations related to gas, tissue and nitrogen laws, they do not take into consideration the actual physiological model of the specific diver. More specifically, they do not consider the actual physiological stress associated with a potentially high-risk profile.

Some diving profiles are more stressful on our physiology and create additional, unnecessary risks to our diving fun. Profiles that involve several partial ascents and descents are called 'Saw Tooth' profiles. Profiles in which the first part of the dive is shallower and the last part of the dive is deeper are called 'Reverse Profiles'. Performing repetitive dives in which the dives are progressively deeper is another example of reverse profiles. These types of profiles are especially hazardous because while diving tables and dive computers perform the math very well they do not account for the added physiological stress and additional nitrogen loading that these dives incur. Always make your deepest dive first and plan each successive dive so it is shallower than the dive proceeding it. Maintain proper ascent rates (no faster than 30 ft. per minute to the 30 ft. safety stop ) and reasonable decent rates (no faster than 65 ft. per minute) by using your time in-depth monitors properly.

Because diving certifications do not expire and refresher or advanced training is not a requirement many experienced divers are finding themselves performing high-risk profiles without their knowledge. Most divers learn to dive on basic tables. Unfortunately, the emphasis on the basic table rules is often lost when moving to a dive computer. A high-risk profile can still be well within the no decompression limits according to the computer or the tables but that does not necessarily make it OK. The basic dive rules exist to add "built in" safety factors. What many divers may not realize that the basic dive profile rules still apply even though the math may say it's OK. Slow ascents, proper safety stops, surface intervals of the appropriate duration and following the other table rules apply more now than ever.

The advancements of technology have made it easier and safer to dive than ever as long as you follow the rules. Consider digging that old dive table from the bottom of your gear bag and reviewing the table rules on the back. Most agencies are very consistent on the main points.

NOW THAT IT'S UNWRAPPED
The holidays are that time of year for rejoicing with family members, friends and gift giving. Some you may find that special scuba item from your wish list under the tree this year. After you have unwrapped your presents, is important to properly store that new piece of equipment. Here are few tips on storing your gear so it is ready for your upcoming diving adventure. Factory Packaging is not necessarily designed for long term storage.

REGULATOR SYSTEMS: Regulator packaging is designed for presentation and protection during shipping and while on shelves. It is not necessarily an ideal place to keep your regulator in between dives. Regulator hoses should not be kinked and rather coiled loosely or hanging freely. Make sure the regulator dust cap is firmly in place. While a garage is a popular place to store equipment is one of the worst places to keep gear. Regulator hoses and some internal components can be subject to accelerated corrosion caused by car exhaust fumes and exposure to Ultraviolet rays. Excessive heat and cold can also affect and/or damage the regulator system. A spare closet in a cool dry place can be a good choice. It is also a good idea to test out the regulator before putting it away . Even if it is only to simply put it on a cylinder and give it a few good breaths. Some manufacturers include warranty paperwork that needs to be filled out and sent in. Most require it within close proximity to the actual purchase of the regulator for warranty validation.

BUOYANCY COMPENSATORS: After you have wandered around the living room wearing your new BC (much to the frustration of your dinner guests), test out the power inflator and the oral inflation valve. (Do not test it out on your guests!) Make sure all of the dump valves are working correctly and fully inflate the BC to check integrity. When you are ready to put it away add a small amount of air. If you're going to hang your BC be sure to use a wide hanger that will not cause creases or dig into the material. Do not put heavy objects on top of the bladder as this can cause punctures and/or weaken the material over time. If the BC has a warranty card fill it out and send it in.

DIVE LIGHTS WITH ALKALINE BATTERIES: Dive lights are very common gift items. Depending on when you plan to use your dive light, it may be a good idea to take the batteries out and store them separately. Even brand new batteries can leak inside the housing. Unscrew the lens cap which will alleviate the pressure on the O-ring. Remember to properly tighten it back down before you go diving to prevent the light from flooding. The life of neoprene and rubber goods including parts like o-rings can be extended by storing them in an airtight bag.

WETSUITS AND NEOPRENE ACCESSORIES: Storing a wetsuit (or any kind of neoprene material) folded can cause permanent damage to the material over time. A fold will actually cause the cell walls of the insulating nitrogen bubbles to break down. This creates a spot with less of an insulating factor because the air pockets are damaged. These are often referred to as cold spots and preventable with proper care and storage. It is also important to avoid laying something heavy on top of the neoprene which will have the same effect. Even accessories like hoods, boots, and gloves should be stored in a way that does not cause creasing or put weight on the materials.

DIVING KNIVES: A surprisingly large amount of damage to equipment is actually caused by storing it a diving knife near it. Pinholes in regulator hoses and Buoyancy Compensators can be caused when a knife is left out or accidentally unsheathed. Securely store your knife in its sheath. If necessary wrap the knife straps around the grip and then back around the sheath. Use knife oil on the blade to prevent corrosion. Many divers store their knife in an accessory pocket to aid accessibility when getting geared up and prevent it from damaging other pieces of gear.

Take care of your equipment and it will take care of you!

SAC RATE
Knowing your SAC Rate (Surface Air Consumption Rate) is a valuable piece of information in the dive planning puzzle. Scuba divers, (especially beginning divers) more often exhaust their air supply before coming close to no decompression limits. Being able to estimate how long a scuba tank might last at a given depth will increase the overall safety of the dive plan.

To determine how much air a diver will use at a given depth, it is first necessary to determine a divers Surface Air Consumption (SAC) rate. As an example: A diver at 33 fsw (feet of sea water) uses 500 psi of gas in 10 minutes. Essentially, the diver is using 50 psi per minute. Taking a trip back to basic scuba class...33 fsw is 2 ATAs (Atmospheres Absolute). If the divers uses 50 psi per minute at 2 ATAs, then the same diver will use 25 psi per minute at the surface (1 ATA). At 66 fsw the same diver would use 75 psi per minute (3 times the pressure / 66 fsw = 3 ATAs) and so on. The process becomes slightly more complex if Depth Consumption Rate (DCR) is determined at a depth that is not in even atmospheres. (Not at 33, 66, 99 fsw etc.) In this situation we use a formula that is simply an adaptation of Boyle's Law to determine our SAC rate:

SAC Rate = (DCR x 33) / (Depth + 33)

Practically applied: A diver performs a 50 foot dive for 25 minutes and uses 1700 psi of air. (Air used is determined by subtracting ending pressure from beginning pressure) To determine DCR (Depth Consumption Rate) divide the air used by dive time. In this example the DCR is 68 psi per minute.

Applying this to the formula: SAC Rate = (68 x 33) / (50+33) SAC Rate = 2244/83 or 27 pounds per minute.

To apply the SAC rate to any profile turn the equation around to determine DCR for any depth:

DCR = SAC Rate x (Depth + 33)/33

Assume a diver has a SAC Rate of 25 psi per minute. The buddy team plans to dive to 75 feet and plans to use 2000 psi. Always remember to factor in a margin of safety and reserves for safety stops. The team needs to know hoe long it will take to use the 2000 psi at 75 feet so they can plan accordingly. Applying this to the equation:

DCR = 25 x (75 + 33)/33 or DCR = 25 x 108/33 or DCR = 81.81

This means at a depth of 75 feet, the diver will use 81.81 pounds of air per minute. Dividing this into the 2000 pounds this amount of air would last 24.4 minutes.

It is important to note that SAC Rate takes into account the assumption that you are exerting the same amount of energy at any given depth, and you are using the same size tank as you used when calculating your DCR. Under strenuous diving conditions, you will consume more air than relaxed. Some divers use different rates for each diving activity, i.e. spear fishing vs. taking pictures. Also remember that smaller cubic feet cylinders will not last as long even though they are both filled to the same pressure.

FIELD CARE & REPAIR: DIVE SAVING TIPS THAT CAN SAVE THE DAY
Even the best maintained system can encounter and infield problem with normal use. Proper servicing, an effective predive systems check and post dive care are the best way to prevent equipment problems. If you are a frequent diver your equipment may require servicing more than once a year. Equipment should also be properly serviced prior to diving after any long period of inactivity. Below are some popular tips from our own staff's field experiences. REMEMBER, each and every scuba system is different! These tips are not a substitute for proper servicing, maintenance or professional troubleshooting. Diving Safety is no accident.

CARE FOR YOUR SPARES: A proper spares kit is an important part of any diving system. Just like any other part of the scuba system, a spares kit post dive maintenance and restocking if necessary. It is also important to make sure that the components of the spares kit actually fit your equipment. As an example not all masks and fins are the same. Some spare straps do not fit certain types or are not long enough. It is also important to check the integrity of the straps as they often corrode or become damaged. One of the most frustrating infield problems is a spare kit full of unusable spares. If you do use a spare make sure to restock it. It is also a good idea to include back up hose retainers and console clips. These items occasionally "vanish" never to be seen again. This will avoid unnecessary equipment damage from dragging hoses.

FREEFLOW: Sand is a common enemy of the second stage. When gearing up for a beach entry it is not uncommon to get sand into the housing. This can cause the regulator to free flow, even though it just passed the pre dive check five minutes ago. Of course the best way to deal with this is prevent it entirely, however here are a few things to try. Rinse and submerge the second stage in fresh water shaking it vigorously. The back and forth, up and down motion combined with the water can likely flush out the loose sand. After you have done this a few times, depress and release the purge button. This will cause the demand lever to move which may free up the guilty particles. Perform a complete predive check again remembering to turn the air on slowly. A proper pre dive check should include checking the integrity of the diaphragm in the second stage. To do this: Fully assembly the regulator system on the tank, just as if you were about to turn the air on. Before pressurizing the lines, test each second stage by inhaling through the mouthpiece. You should feel the demand lever depress and get no air at all. If you do get air, there is a leak somewhere. This leak could cause the regulator to breathe wet or flood depending on the size of the leak. Check to make sure the first stage is seated correctly and amply tight on the tank. If the system is seated properly and there is still a leak something is very wrong. The system in likely unsafe to dive.

ORING OH-NOS: A properly assembled regulator has the hose fittings tightened enough to maintain a seal but not too tight so as to damage the first stage or hose end fittings. Because of this it is not uncommon for a hose to loosen in the field (before pressurization) causing a leak. If you do not have a proper size (or adjustable) wrench it may be possible to hand tighten the hose to a safe operating point. Turn the air off and purge the air from the lines. Take a look at the o-ring paying specific attention for signs of wear or damage. If the o-ring is damaged this will not work. Tighten the hose until it does not turn any more. Then SLOWLY pressurize the lines and check for leaks. If there is a seal with a full tank of air on than that problem has been temporarily avoided. Perform a complete predive systems check again. A word of caution when using wrenches as over tightening can cause permanent equipment damage. Some fittings actually require the use of 2 wrenches. Failure to do so can cause irreparable equipment damage and should only be done be certified professionals.

STORAGE WOES: Many divers will perform a detailed check and assembly prior to arriving at the dive site. After this check is done, the pack the gear to be ready for the dive day. It is at this point that a few moments of extra care can ensure a successful dive day. Even though the equipment will be used relatively right away, the same rules for long term storage apply. Sharp items (like dive knives) should be packed separate from the system. If the knife as an example, was to come loose from it's sheath equipment could become damaged in transport. Heavy items like weights should not be placed on top of more fragile items. It is also a good practice to pack in a relative order as to when the equipment will be needed. A dive skin would be donned before a wetsuit, so place the skin on top and so on. This help make gearing up easier and lessens the chance of forgetting something. Following proper storage procedures will certainly minimize infield equipment problems.

COMPUTER STOPS: Dive Computers like any other piece of dive gear are effected by corrosion for multiple reasons. Unfortunately, it is often at the dive site that the problem is realized. Depending on the problem, try removing the battery (ONLY if you have a computer with diver replaceable batteries) as outlined in the manufactures manual. Pay special attention to the o-ring(s) being careful not to damaged them. Some manufactures require the o-ring to be replaced each time the battery compartment in opened. So, not having a spare o-ring can pose another problem. Gently clean the contacts with a soft cloth being careful not to damage them. Reassemble and perform a complete predive check. Make sure the low battery warning has not come on as some computers encounter performance issues with very low batteries rendering them undiveable until the battery is replaced with a new one.

KNOW THE RESPONSIBLE DIVER CODE
Do you know the responsible diver code? Introduced in the early 90s, this set of six concepts can make the difference. Before taking the "plunge" with a new buddy, review the Responsible Diver Code together. Remember, a poor attitude only gets worse with depth.

As a responsible diver, I understand and assume all the risks I encounter while diving.

My responsible diving duties include:

"THERE IS A REASON FOR IT..."
When first learning to dive, your instructor probably reminded you to open the tank valve on all the way and then half a turn back. While this is now a standard dive practice, did you know that there are actually very real reasons for it.

The dive scenario: Diver Don hastily gears up and jumps in. When he reaches the bottom he notices that his pressure gauge needle drops to almost empty and then returns to about 2800 psi. Quite concerned about the functioning of his equipment, Diver Don and his buddy abort the dive. Back at the beach Diver Don tries to figure out what is wrong with no success.

While this sounds pretty scary, in this case, it could have been prevented and/or rectified by simply opening the cylinder valve all the way. Because the valve had not been turned on all the way, the regulator was not receiving optimal amounts of pressure. When Diver Don would take a breath the pressure gauge reading would drop. The needle would return to the actual cylinder pressure on the exhalation cycle. This same problem can also occur with digital pressure gauges and diving computers and the pressure sensors work in similar ways. Some valves are easier to turn than others, so it is important to pay extra attention. After all breathing is an important part of a successful dive day.

Continuing along with this concept, when fully opening a valve do not over open the valve knob. It may become necessary to shut down the cylinder, (such as in the case of a leak or rupture). That half a turn back keeps the valve knob moving freely and also reduces wear on the seals. As always, keep your gear in proper working order with proper care and maintenance.

"LOOSING IT ON THE BOTTOM
Solo Diving: That dreaded word never to be spoken within earshot of a Dive Master. The practice will get you banned from dive boats and kicked out of dive clubs. We are taught "never" to dive without a buddy, and that is about where it becomes complicated.

The main purpose of the buddy team is to assist each other in routine and possible emergency situations. An effective buddy can add to the overall enjoyment of the dive and make gearing up a breeze. In an emergency situation the "dependent diver" (A.K.A. diver in need), becomes reliant on the other member of the buddy team. When performed properly, the emergency will be minimized. While this sounds easy enough, there are more solo divers than anyone is willing to admit. Less experienced divers can often find themselves in a solo dive situation because they simple "relied" on a more experienced diver. Often "experienced" divers keep up appearances by agreeing to start and end the dive with a buddy but little more.

Two divers can actually be performing "solo dives" because their skill levels are unequal. In this scenario the less experienced diver can be helped by his more experienced buddy, but the reverse it not the case. The more experienced diver is actually in practice performing a "solo dive". Another scenario is a group dive, without specified buddies. Because no one has established who assists who, the group is actually performing several solo dives on one reef. This may seem like a small point, and it is until something goes wrong. In this example, not knowing who your buddy is can waste valuable seconds deciding and/or even finding your buddy.

So what is a diver to do? Below are 4 quick tips to ensure your buddy is "there" for you."

DISPLACEMENT - THE OTHER REGULATOR CLEARING TECHNIQUE
As certified diver's, clearing your regulator is a long since conquered skill. Many of us prefer to simply exhale, others like to use the purge button and many use a combination of both throughout their dive. Did you know there is third way to clear the regulator that works in almost any situation? Unlike exhaling, which demands you have air to expel or purging which assumes you have access to the purge button (and it is functioning) "displacement" is a third method that you should add to your skill set. (It is also a part of some basic open water certification programs.)

As with any diving skill or technique, always practice in shallow water with a competent diving partner under controlled conditions, ideally a pool.

SKILL DESCRIPTION:

8 GEAR SAVING CARE TIPS
The dive is over and all that gear needs to be rinsed, packed and prepped for the next dive. Here are some beyond basic tips that will increase the life of your gear and make caring for it even easier.

5 WAYS TO SAFELY SAVE A DIVE
At some point, every diver is faced with the frustration of making the decision to call a dive day. This can be a big disappointment. This weeks' topic includes some valuable tips that may safely save a dive.

Arriving at a dive site only to find the conditions less than favorable is the number one reason for most dive cancellations. This is where knowing your environment can really pay off. Weather conditions that can make a site undiveable can also make another (not far off site) a pleasure. The trick is knowing your area and how it is affected by environmental conditions. Consider this before packing up and heading home. As always, if you are not sure, nor have reliable sources to advise you it is best to dive another day.

Relax and Replan: Factors beyond your control can trash the perfect dive plan. Taking the time to properly plan is very important. When factors change, all is not lost. Often only a few small modifications to the dive plan are necessary. Before overreacting to the Dive Masters announcement of the alternate site, relax! Consider what has really changed: Is the depth different? By how much? You may even have planned alternate depths (a complete dive plan does have those) and not need to make any changes at all. Most importantly think rationally and calmly using the knowledge you have gained from your training and experience. If however, the logistics of the dive have changed beyond the scope of your abilities speak with a professional onsite. If you do not feel comfortable, sitting this one out may be the best decision.

Make a predive snorkel. Before gearing up and jumping in make a "Snorkel Dive". This is a great way to safely survey most situations. Just a few minutes in the water can take the mystery out of bottom formations, currents, water temperature and more. Surface conditions can be misleading and it is easier to respond while wearing mask, fins snorkel etc. than in a full scuba system.

Consider the time. If you will be diving later in the day plan in advance to bring dive lights and night diving gear. Gearing up delays can easily cause an unplanned dusk dive. By already having lights with you, the buddy team can compensate and still make the dive (provided the sight is acceptable for dusk/night diving).

Wait it out. The ocean is always on the move. Tides and weather are constantly changing affecting your dive for the better or worse. Sometimes you can wait the conditions out, depending on the site. As an example major changes in tides can produce undiveable currents. A short time later the conditions can become much less severe and the day is saved. Know your area, check tide tables, use your best judgement and always be safe. Remember to dive or not to dive is a choice that is ultimately up to you. When in doubt, just stay out!

19 RULES FOR SAFER COMPUTER USAGE
When used correctly, a Personal Dive Computer will make diving easier and safer. It is important however to remember that Dive Computers are just performing mathematical calculations based on their programming. They do now how you feel and will not dispatch the "Scuba Police" to stop you from staying too long or going too deep. Below are 19 rules for safer computer usage. While some are self evident, there may be a few that even an "experienced" diver may not have been completely aware of!

Read the owners manual: It is amazing how few divers read the information provided by the manufacturer. Each model has its own unique operation and display. Learn the features your computer has and be aware of them throughout your dive. It would be good to know if computer has audible alarms rather than spend a dive "wondering what that annoying beeping sound is".

Never share your computer with another diver: Always have at least one computer per diver. (This applies to all instrumentation too!) Diving depths often vary within the same buddy team.

Plan the dive and read the pre-dive plan as displayed on your computer: The buddy team needs to agree on maximum depth and bottom time. It is also important to verify that the planned profile is consistent with the computers' built-in planning.

Check Operation: Check the unit for proper operation BEFORE entering the water. Many computers require to be turned on before beginning the dive. Some computers will auto shut off if not pressurized within a specific amount of time, (your owners manual should have that info in it).

Look: Carefully and frequently monitor the computer. A computer is only a benefit to the diver who reads it. When in doubt: If one buddy's computer is more conservative (or reading more conservatively) that the other�s always follow the more conservative computer.

Deepest First: An oldie but a goodie...J ust because computers "can" perform the calculations doesn't mean you "should"! Always perform the deepest dive first with progressively shallower repetitive dives. In same, always perform the deepest part of your dive first moving shallower as the dive progresses. Reverse profiles cause unnecessary added physiological stresses which can compromise the overall safety of the diver.

Don't push it: Do not dive a computer to its maximum limits. Individual physiology is not taken into consideration by the computer. Physical predispositions such as lipid tissue content, workload, cold, fatigue, prior injury, and even certain dietary factors can make a diver more likely to "take a hit" (become afflicted with decompression illness).

Follow a slow ascent procedure: Ascend no faster than 30 feet per minute.

Make a safety stop: Even if you are in the "green" perform a 5 minute safety stop at 15 feet. If surface conditions are rough move deeper to 30 feet (max).

Monitor your no decompression limits and time remaining: While many computers can calculate decompression profiles, it does not necessarily mean that the diver is properly trained and equipped to perform such profiles. Additional training is required to reduce the risk factor of decompression profiles. There is no such thing as a "safe" decompression dive.

Always have a back up plan: While it is rare for a dive computer to shut off during a dive, it is still a possibility. If this were to occur the correct procedure is simple: Check your buddy's computer (only to give a general idea of the profile), abort the dive and perform proper ascent procedure (no faster than 30 feet per minute). Then, complete a minimum of 10 minutes decompression (even though your profile is a no decompression profile) at 10 feet. This is more for safety on future dives than it is for the current dive. Do not dive for 24 hours to establish a zero RNT (Residual Nitrogen Time). The alternative to the failed dive computer procedure is to always dive with back-up computer.

Log you dive profiles: Use your log book to record the maximum depth and bottom time of each dive. The information will prove helpful should difficulty arise.

1 Hour Minimum Surface Interval: While shorter surface intervals "can" be performed they add additional risk to dive profiles.

Leave a 12 hour surface interval between dive days: Surface Intervals of less than 12 hours are considered repetitive dives. Take every 4th day off from diving when diving consecutive days: Diving Computers have more difficulty accurately tracking the Nitrogen being absorbed by the slowest body tissues. These tissues usually approach saturation after only several days of repetitive diving.

Be extra cautious if your plans call for traveling to altitude following a dive: Extra safety stops are strongly recommended if a trip to the i.e. mountains follows your dive. If diving at altitude be sure to adjust your computer for the correct ambient pressure. While some computers do this automatically many require diver adjustment. (Back to the point on reading the manual!)

Always allow 24 hours before air travel: Flying after diving is equivalent to a pressure reduction of approximately 8,000 feet. This pressure reduction can bring about DCI (Decompression Illness) in the inadequately decompressed diver.

Keep these rules in mind to better ensure a safer dives. Adapted for this article from text: Open Water Sport Diver, by Edward A. Betts, Copyright ANDI International, Ltd. Oct. 1999. Remember: The advanced features of diving computers are not necessarily proportionate to a specific divers actual capabilities.

RULE OF THIRDS
The Rule of Thirds is a great way to manage your dive plan during the dive by avoiding the "Point of No Return" scenario. When applied properly it also builds in a valuable safety factory reducing the possibility of an out of air situation. To incorporate properly requires little more than basic navigational awareness and of course, you have to look at your pressure gauge.

Simply put, the Rule of Thirds divides the total amount of air a diver has in their tank and applies it to specific phases of the dive. Because air is usually the greatest limiting factor (in comparison to no decompression limits for the average profile) the entire dive, including how far the buddy team swims in each direction becomes based on this.
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