Scuba Tank Safety

There is only one bit of advice you need when you own your own tanks: bring them to a professional for filling and regular inspection.

Tanks are required to be visually inspected once a year, which involves removing the valve and looking inside for signs of corrosion or damage. If the tank is deemed safe, an Evidence of Inspection (EOI) sticker is applied to the tank showing the date of inspection.

hydrostatic test is required every 5 years, which determines the tank’s ability to contain pressurized gas. A certified hydro test facility will stamp the shoulder of the tank below the valve with the date of pass.


An average scuba tank, filled to 3000psi, contains approximately 1.3 million foot-pounds of kinetic energy potential. This is enough to lift a 100-ton locomotive off its tracks and into the air. 
The explosive power of a scuba tank is equivalent to a hand grenade.

This inspection makes it easy for you to know if your rented tank has been properly maintained and inspected. If the hydro test stamp is more than 5 years old or the EOI sticker is more than a year old, don’t accept the tank.

Corrosion is the major culprit in tank degradation. Scuba tanks are filled with very dry air, to prevent moisture from rusting the interior of the tank. That is why certified divers learn never to leave a tank empty. Always leave at least 100psi of pressure in the tank at the end of your dive, so no moisture can get in when valves are opened.

Swim Fins

The creation and advancement of swim fins has become a science. Without them scuba diving is almost impossible; with them scuba diving is a dream of fluid underwater movement. Swim fins allow you to propel yourself through the water with the least amount of energy and effort. When you are fully clothed in your scuba diving attire, including: wet suit, buoyancy compensator, air tank and weights – moving in the water can be almost impossible and extremely tiring. The right pair of fins will allow you to go further and swim faster using the large muscles in your thighs.

There is an incredible selection of swim fins to choose from. There are swim fins shaped like a dolphin’s tail, swim fins with channels like the webbed feet of a duck, split swim fins, curved swim fins, stiff swim fins and flexible swim fins. The choice is almost overwhelming, but advantageous for the wide variety of scuba divers. Each pair of swim fins will perform differently on different people, so you want to choose the right scuba diving fin for you. You want to make sure you choose swim fins that are comfortable to wear, will allow you to kick/swim for long periods of time without cramping your legs and which don’t pinch your toes or heels.

Not all swim fins are made of the same material, but they all must withstand the effects of sun, salt and sand. To ensure your swim fins last for many years you will want to purchase a high quality pair of swim fins.

Swim fins are worn over neoprene scuba booties. The booties offer durable, pliable padding and protection so that you can strap the fins securely and comfortably to your feet. Swim fins have an open back and a thick strap which buckles behind the heel.

Choosing Swim Fins

When shopping for swim fins the most difficult decision you will need to make is between a split fin or a non-split fin. A traditional swim fin is a simple, elongated flat foot extension (like duck feet). Split fins are a newer design where the swim fin is split in two parts by a lengthwise slit. Split fins are more expensive and offer slightly better propulsion. It is up to the scuba diver whether the higher price justifies minimally improved performance. Suffice to say that while split fins are a nice luxury a properly fit non-split fin is perfectly effective.

Buy your swim fins and scuba booties at the same time. You will want to try both on at once and be absolutely certain they are comfortable together. Once you have both swim fins on sit in a chair and flap them around vigorously. A well-fitting swim fin and a scuba booty will not rub or chafe, it will be snug and secure, but not tight.

The other feature to insist upon is a good strap. Fin straps should be attached on both sides with quick-release buckles which allow you to loosen the strap without detaching it. When loosened, your foot should slip out easily and when tight should be snug and secure. The straps should be thick and durable and the buckles should be equally durable and release with just a little push – easily, but not too easily.

Swim fins come in sizes similar to your shoe size. They should fit like your shoes, snugly without pinching your toes or heels. If your swim fins are too large they will easily be kicked off during a dive. If you plan on wearing scuba booties with your swim fins you need to try on your swim fins while wearing your scuba booties to ensure your swim fins fit properly. You will most likely need to get swim fins that are one size larger if you plan on wearing scuba booties with your swim fins.

Swim fins will have one of two types of foot pockets; full-foot pocket fin or open-heel pocket fin. The full-foot pocket fin encloses your entire foot just as a slipper encloses your foot. The open-heel pocket encloses the front portion of your foot and uses a heel strap to secure the fin to your foot. The heel strap on the open-heel pocket fins can be either adjustable or non-adjustable. Non-adjustable heel straps have an amount of elasticity and hug your heel very closely. Adjustable heel straps have buckles on either side of the foot which allows you to adjust the swim fin to fit your foot, whether you are barefoot or wearing booties. Most scuba divers who dive in cold water prefer the adjustable swim fins because they are easier to use and an easier fit when wearing booties.

Do many scuba divers write on their fins?

No, actually it’s not that common. Most people buy new fins and keep them looking clean and new-looking. Fin graffiti is, as far as I know, a fad that may have originated in Hawaii, or perhaps it started elsewhere and was just more popular among Hawaiian divers than elsewhere. Depending on the society you keep, a pair of well-decorated fins increases your scuba-cred.

The best markers to use on plastic and rubber are the ultra-permanent “Sharpies”. Some divers write the names of famous reefs on their fins after they dive them, a practice reminiscent of the WWII flying aces stenciling symbols on their planes.

Other divers go for a kind of tattoo-flash embellishment on their fins that would look just as fitting on the bottom of a skateboard. No major manufacturers have released “flame-job” fins or “8-ball” fins or highly stylized designs, so the decoration of scuba fins is still a home-grown artistic pastime.

Scuba Booties

Scuba booties are like neoprene socks, some have a zipper up the side and hard bottoms so you can walk over rocks and other hard surfaces. They protect your feet from cuts, burns and abrasions when walking on rocky beaches, rough boat decks and hot pavement. If you are a cold water scuba diver they will help keep you feet warm. Booties can also prevent blisters from the heel strap of your fins rubbing directly against your heel when walking and swimming.

Choosing Scuba Booties

You will want to purchase your swim fins when you purchase your scuba booties. If you plan on using booties with your swim fins you will most likely need to purchase your swim fins in one size larger. You will need to wear your scuba booties when trying on swim fins to ensure your fins are the correct size.

Scuba booties come in sizes similar to your shoe size. They should fit like your shoes; snugly, without pinching your toes or heels.

Scuba booties also come in different thicknesses for different water temperatures. If you are diving in tropical waters a lighter neoprene is preferred. If you are a cold water diver you will want your booties to be made of thicker neoprene to keep your feet warm.

Scuba booties are either pull-on or zippered. Pull-on booties are literally just like your socks; they pull on your feet and conform to the shape of your foot. Depending on the thickness of your scuba booties they may be difficult to get on and off. The thicker the neoprene the more difficult they will be to put on and take off. If you are a cold water diver you will need thicker neoprene and may want to purchase zippered booties. These are much easier to put on and take off. If you do choose zippered booties check to make sure the zipper has a backing that will prevent cold water from entering the boots.

Maintaining Scuba Booties

The key to keeping your scuba booties clean and free of odor is proper maintenance after each dive. These maintenance procedures will help to keep your booties in good shape for many years of scuba diving:

  1. Rinse your booties in clean, freshwater after each dive and allow them to dry thoroughly before storing. After a div, your booties will be covered in a salty residue and/or dirt. This must be rinsed clean to prevent the neoprene from degrading. Your scuba booties must be completely dry before storing to ensure the neoprene stays clean, odor-free and free of mildew or mold.
  1. Scuba bootie zippers should be lubricated occasionally to prevent degradation of the metal or plastic.
  2. Always store your scuba booties out of direct sunlight. Direct sunlight will break down the neoprene after years of exposure.
  3. Periodically machine or hand-wash your scuba booties. A good rinse after each dive helps to keep your booties clean, but to ensure there is no residue or grit left on your booties you must properly clean them on a regular basis. You can purchase a commercially prepared neoprene shampoo, zipper lubricant/desalter and a neoprene sealant to thoroughly clean and seal your scuba booties. A commercial shampoo and sealant are specifically manufactured to care for your neoprene and is the recommended method for proper maintenance.
  4. Any holes in the neoprene on your scuba booties can be fixed using a commercial wet suit cement.

Scuba Mask Maintenance

Almost all scuba diving gear requires some preparation before it can be used. When you bring home your scuba mask, you will notice an oily film on the lens of your mask and sometimes on the strap of your mask. Most manufacturers rub a light oil onto the silicone to help protect the silicone during shipping. You need to remove this film before you use your scuba mask, otherwise your mask will continually fog while diving. An oily film on your mask will prevent it from sealing properly or the mask may slip off your face during a dive. To clean your scuba mask, apply a pea-sized drop of toothpaste, not gel, to the inside of the lens. Using your fingertips rub the toothpaste in a circular motion around the entire surface of the lens. Do not use your fingernails; this may scratch the lens of the mask. Rinse with clean water and repeat until the film is completely removed. You can also rub toothpaste up and down the strap to remove any film. Always rinse your mask thoroughly after cleaning.

The key to clear vision, while scuba diving and keeping your scuba mask in good condition, is proper maintenance during and after each dive. These maintenance procedures will help to keep your mask in good shape for many years of scuba diving:

  1. Use a defogging solution before every dive, even when diving more than once in the same day. This will prevent your scuba mask from fogging during a dive. You can purchase a commercially prepared defogging solution from any reputable scuba diving retailer. Squeeze a drop or two onto the inside lens of your mask and gently rub the solution around to cover the inside completely. Dip your mask briefly into water, swirl the water around the inside of your mask very quickly and empty the water from your mask. A quick rinse will remove any excess defogging solution from the inside of your mask. You do not want to get defogging solution in your eyes, especially while diving, since it can cause stinging and irritation. If you don’t want to use a commercially prepared defogging solution you have a defogging solution readily available and it’s free, your saliva. Your saliva will prevent your scuba mask from fogging just as well as any commercial defogging solution. The enzymes in your saliva stick to the lens of your mask like a commercial defogging solution and you will never find yourself without a defogger while on a dive.
  2. Never lay your scuba mask face-down on any surface. Salt, sand and grit will scratch the lens of your mask. Always place your mask face up when you are not wearing it or if it is not in its hard case.
  3. Rinse your scuba mask in clean, freshwater after each dive and dry it thoroughly before storing it in its hard case. After a dive, your mask will be covered in a salty residue and/or dirt. This must be rinsed clean to prevent the silicone on your mask from degrading. Your mask must be completely dry before storing it to ensure the silicone stays clean and odor-free.
  4. Always store your scuba mask in its hard case. If your mask did not come with a hard case purchase an after-market hard case. This will protect your mask from dirt and abrasives and protect it while traveling. Always store the case out of direct sunlight. Direct sunlight will break down the silicone after years of exposure.
  5. Periodically repeat the toothpaste treatment to keep the lens of your scuba mask clean. A good rinse after each dive helps to keep your mask clean, but to ensure there is no residue or grit left on your scuba mask you must properly clean it on a regular basis.

Choosing a Scuba Mask

Scuba masks are available in a wide variety of shapes and sizes each offering a varying field of vision. The two most common styles of scuba masks offer either a 3-pane or a 4-pane lens. The 3-pane lens offers a single front lens with left and right side windows. A 4-pane scuba mask separates the front lens into two pieces and includes the left and right side windows. The style of scuba mask you choose will depend on your level of comfort with your field of vision while wearing the scuba mask. Some scuba divers prefer the single front lens because the frame does not impede their vision while looking side to side; other scuba divers prefer the 2-pane front lens because the style and comfort is similar to wearing sunglasses.

The shape of the scuba mask and the silicone skirt on the mask must conform to the shape of your face to provide you with a comfortable fit. Ensuring the silicone skirt is a high-grade, flexible silicone can help to ensure the scuba mask conforms to the shape of your face and the long life of your scuba mask. Some people are allergic to different types of rubber, if you have an allergy to rubber, be sure to choose a silicone scuba mask because silicone is hypoallergenic. Always talk to your scuba diving gear retailer about the alternatives available to you.

When trying on scuba masks you will notice the different shapes of the nose pockets. The nose pocket protects and cushions your nose, helps to keep your scuba mask from fogging during a dive and helps you to maintain equalization. Ensure the size and shape of your nose pocket is comfortable; not too tight and not too large. This will improve not only the comfort of your scuba mask, but your ability to purge your mask efficiently.

There are increasingly different styles of scuba mask straps on the market. You may like the factory issue strap on your scuba mask or you may want to purchase a separate strap. Scuba mask straps are available in a single strap or a double strap design. The single strap should wrap around the centre of the back of your head. The benefit of the double strap is that you can position the top strap on the upper part of your head and the bottom strap on the lower part of your head to offer extra stability and comfort. Most scuba mask straps are rubber or silicone and fasten with a post-hole belt enclosure. Newer scuba masks offer a slide-lock type enclosure, which allows you to adjust the scuba mask quickly and easily when wearing the mask.

Scuba masks are constantly improving. If you wear prescription glasses or contact lenses on a daily basis you can purchase a scuba mask without having to wear your glasses or contact lenses under your mask. Many manufacturers will create custom scuba masks which include your prescription in the front lens.

A good sign you have chosen the right scuba mask for your face is when the mask stays on your face comfortably without using the straps to hold it in place. You should try this simple test with each scuba mask you try on for the first time:

  1. Place the scuba mask over your eyes and mouth ensuring the mask is in the correct position.
  2. Take a quick, light breath in through your nose and immediately start to breathe through your mouth as if you are scuba diving. This will create a slight suction between the scuba mask and your face. The scuba mask should stay on your face. If you must push the scuba mask against your face, or inhale repeatedly to help the mask stay on your face, the mask is not a good fit.
  3. Keep the scuba mask on your face for approximately one minute. This will help you to determine how tight the seal is and how comfortable the mask is on your face.
  4. Exhale gently through your nose to release the seal on your scuba mask and remove the mask from your face.

There should be no mark on your face from the scuba mask. If there is a red line around your face from the seal of the mask, the seal was too tight or the mask is not the proper size for your face. Try the test a second time. If you still have a red mark on your face after you remove the mask, you need to continue your search for a scuba mask. Remember, a good scuba mask is one that’s comfortable, doesn’t leak and is easy to use.


Scuba Masks

Your scuba mask provides your view to the vast underwater world of the ocean. There is an endless view of coral, fish and sea mammals in our oceans and seas and you will want, and need, a high quality scuba mask to allow you many years of underwater viewing enjoyment. Scuba masks come in an endless choice of style and color, but there are many things to consider when purchasing your first, or tenth, scuba mask, including: field of vision, a high-grade silicone skirt for a lasting and comfortable seal, comfortable nose pocket and a high-grade, flexible silicone strap and strap fasteners.

Buying a high quality scuba mask and its proper care will ensure the longevity of the mask. Any scuba diving gear retailer should have a wide variety of scuba masks available for you to choose from. Every face is different and every scuba mask does not fit every face. You should try on a variety of scuba masks, of different shapes and sizes; to ensure the scuba mask you purchase fits you properly and will be comfortable for long scuba dives. If you have trouble finding a scuba mask or are unsure about what size of scuba mask you need your retailer should be able to help you find the right scuba mask.

There are many scuba masks available. Take the time to choose the right scuba mask for you. Your eyes will appreciate it and you will enjoy the beauty of scuba diving that much more.

How to tell when a mask is fitted right

Here’s a useful test that is easy to do. Press the mask to your face, without strapping it on. Just by breathing in with your nose, you should be able to suck the mask onto your face and walk around without it falling off. That proves that you have a good seal around the edge.

My scuba instructor told me to spit in my mask. Is he kidding?

No! He’s not kidding! Saliva works very well as a mask defogger, for reasons that have never been adequately explained. Something in the saliva will keep the mask from fogging up. Many divers swear by it, and will use nothing else. There are commercial mask defoggers available, usually sold in little eyedropper bottles. A popular recipe for mask defogger is 5 parts water to 1 part biodegradable dish washing solution. Diluted glycerine is also effective.

See also:

Scuba Regulators

The scuba regulator is the fundamental invention which makes recreational scuba diving possible. The regulator reduces the pressure of the air coming from your tank to the ambient water pressure and delivers it to your mouth for you to breathe.

The scuba regulator has two parts: a 1st stage and a second stage connected by a hose. The 1st stage connects right to the tank; the 2nd stage is the contraption behind your mouthpiece. Both have an important function in regulating air flow throughout your scuba system.

First stage scuba regulator

pictured: Mares V16 Proton Metal Regulator: first stage

The 1st stage is a valve that lowers the air pressure coming from the scuba tank. It is really similar to a water tap; without a tap the water pressure pushes the water out of your faucet at a gushing full force. With a tap you can control the rate of flow. The 1st stage scuba regulator does the same thing: instead of the air gushing out at 2000psi it reduces the flow to about 140psi.

Inside the first-stage scuba regulator are pressure chambers separated by valves or pistons. Depending on the ambient pressure (which changes according to your depth) the first stage will change the rate of air flow. It is like a tap that turns itself up and down depending on your depth. At higher pressures it opens up; at lower pressures it closes. This ensures that all devices using your air (like the hose used to inflate your BCD) function properly at any depth.

When you breathe in through the mouthpiece you suck air out of the breathing chamber. This lowers the pressure inside the hose below the ambient water pressure. The water pressure pushes in a diaphragm or piston, attached to a valve, to open the air flow; letting in enough extra air to balance the air pressure again. Doing this means the air pressure flowing to your mouthpiece is always balanced against the ambient water pressure.

The 1st stage will have several outputs coming out of it. Some are at high pressure – these go to your tank pressure gauge. The others are at the lower, controlled pressure – these go through the hose to your second stage, your spare regulator (a.k.a. the “octopus”) and to the inflator for your BCD or dry suit hose.

Second stage scuba regulator

pictured: Mares V16 Proton Metal Regulator: second stage

The second stage regulator takes the manageable pressure coming from the 1st stage through the hose and delivers it to your mouthpiece in a way that is comfortable to breathe. Where the 1st stage is only concerned with letting air flow into the hose the 2nd stage has more complex machinery which handles both inhaling and exhaling through the same mouthpiece.

Like the first stage the 2nd stage scuba regulator uses a diaphragm or piston to open a valve. Breathing in from the mouthpiece reduces the air pressure inside the chamber, water pressure pushes the diaphragm in, which opens the intake valve. When you stop inhaling the pressure in the chamber balances and the valve closes. The result is an air delivery system which supplies air only when you are inhaling and does not leak air constantly through the mouthpiece. A well balanced and well-maintained scuba regulator does its job so well that breathing feels natural and effortless despite the all mechanics involved.

The second stage scuba regulator also has a purge or exhaust valve, which lets your exhaled air out of the chamber, but doesn’t let water in. When you exhale into the second stage scuba regulator the pressure inside the chamber becomes greater than the ambient pressure. The exhaust valve is a simple one-way valve which lets this air escape.

The second stage scuba regulator also has a purge or exhaust valve, which lets your exhaled air out of the chamber, but doesn’t let water in. When you exhale into the second stage scuba regulator the pressure inside the chamber becomes greater than the ambient pressure. The exhaust valve is a simple one-way valve which lets this air escape.

A second stage scuba regulator also has an “emergency” or “purge” button which forces the intake valve to open. When the purge button is pressed air will flow continuously into the chamber and escape either through the mouthpiece or the aforementioned exhaust valve.

See Also:

Scuba Air Pressure

Air is massive. All around and above us we are “swimming” in air and the weight of the air above us exerts pressure on everything in it. We do not notice or feel the air pressure around us because our bodies are compressed and exert an equal force back.

The weight of the atmosphere exerts a pressure of 14.7 psi at sea level. In other words, a 1 inch column of air as tall as the atmosphere (about 50 miles) weighs 14.7 pounds. This unit is called 1 Atmosphere of pressure or 1 ATM.

Scuba divers are concerned with pressures in tanks, in heads, in masks and under the water. We know that water is much heavier than air, so it exerts higher pressures with less volume. A cubic foot of water weighs 62.5 lbs, whereas a cubic foot of air weighs 1/12 lb. Sea water is even heavier – a cubic foot of sea water weighs 64 lbs. To exert 14.7 psi (1 ATM) it takes 50 miles of air, whereas it only takes 33 feet of water to exert the same pressure.

The point to remember is that at the surface we are not at zero. We start descending with 1 ATM working on our bodies. At 33 feet underwater we are at 2 ATM and at 66 feet deep we reach 3 ATM.

Let’s suppose you fill a balloon with 24L of air. Let’s take it scuba diving.

DepthPressureVolumeAir Density
sea level1 ATM121x
33′2 ATM62x
66′3 ATM43x
99′4 ATM34x
132′5 ATM2.45x

You see that the volume of the air changed the most between 0 feet and 33 feet, where it was squished to half of its previous size; a loss of 6L. Descending from 33 feet to 66 feet changed the volume by only 2L. As our air goes deeper the relative compression decreases. You will experience this effect firsthand when scuba diving; the first 15 feet is when you’ll feel “the squeeze” as all air spaces (lungs, sinuses, ear canals, the air in your mask, intestines and even bits of air trapped in your teeth) are compressed to half of their sea-level size. When descending you need to compensate for that loss of volume and “reinflate” your body by equalizing your ears, exhaling into your mask (which will literally suction itself to your face). You also need to add air to your BCD to maintain buoyancy. Once you’re past 15 feet it gets easier and once you’re below 40 feet you might hardly feel the difference in pressure at all.

The reverse holds true when ascending to the surface. All the air spaces will double in size in the last 33 feet; this means you need to leak out air as you ascend, bubbles will escape from your mask and you need to release air from your BCD; lest it inflate like a balloon and send you bobbing quickly to the surface (and probably give you the bends while you’re at it).

Scuba Air Tanks

A scuba tank, also called a scuba cylinder, is constructed out of either steel or aluminum. Aluminum tanks are more common and less expensive, but more prone to denting and wear. Most dive gear shops will only have aluminum tanks for rent, so it is good to become used to their size, weight, shape and buoyancy.

Steel scuba tanks are a little more expensive, but they are far more durable. It is said that a properly maintained steel tank will last longer than the diver who wears it. The caveat with a steel scuba tank is that it will rust and a steel tank user needs to periodically inspect their tank for rust, but rusting can be somewhat avoided with proper care.

Whether you get aluminum or steel, regardless of the actual physical tolerance of the tank, when you get your tank filled it will be filled to 3000 psi (see the Scuba Physics section for explanation). The capacity of your tank is measured in pressurized cubic feet; in other words how many cubic feet (or liters) of air can be stored in the tank at 3000psi? An average tank holds about 80 cubic feet of air, though tanks range in size from 65 to 100 cubic feet. Extra-large and extra-small scuba tanks are available in size from 120 cubic feet down to the tiny 6 cubic foot “pony tanks”.

The size of scuba tank you need is decided by the amount of air you will need; the amount of air you need is determined by your size, the size of your lungs, your fitness level and other factors. If you are a teen or a petite woman you will be fine with a smaller tank. An average adult will take an average (80 cu.ft.) tank. Large men who breathe deeply might want the largest tank available.

An 80 cu.ft. cylinder at 3000 psi contains 80 cu. ft. of air, which is about the size of a small telephone booth. The air in a telephone booth at 14.7 psi (or 1 ATM, which is ambient sea-level air pressure) weighs about 6.5lbs. The air is compressed 204.08 times smaller to fit into the scuba cylinder.

3000 psi / 14.7 psi = 204.08

The air in the tank still weighs 6.5lbs, which is why you can feel the weight difference between an empty tank and a full one. You would feel the same difference lifting the telephone booth full of air, compared with the same booth containing a vacuum.

One kind of scuba cylinder becoming increasingly popular is the pony tank. A pony tank is a little extra tank which straps to your gear, which has separate staged regulators and sometimes gauges as well. In case your equipment malfunctions or you misjudge your air consumption the pony contains enough air to do a proper slow ascent to the surface. A pony tank is usually carried as an emergency backup air supply, not as a means of extending a dive.

Typical atmospheric air is mostly nitrogen (78%) and oxygen (21%) with only a small amount of carbon dioxide (0.03%). Other gases are present in trace amounts: Hydrogen, Argon, Neon, Helium and more.

When you breathe your lungs absorb oxygen from the air, but they also absorb all the other gases as well. The oxygen is used by your body for all its functions, but what about nitrogen? Air has more than three times more nitrogen than oxygen, so your body is dealing with quite a lot of it. The answer is that our body is saturated with inert nitrogen, it offgasses through your skin and quite a lot of it filtered by your organs and passed as nitrates in your urine.

When your tanks are filled for scuba diving they are usually filled with dry filtered air. Pumps and filters remove most of the particulates (dust, pollen, airborne pollutants). Water vapor is also present in air; the amount varying greatly depending on temperature, pressure and weather. Water condensation can rust the inside of a scuba tank, so water vapor is filtered as well. The result is a tank containing a normal mixture of dry atmospheric gases in normal proportions.