How to use less air… or just dive longer

Updated: 30 Jan, 2018

Michael Fineberg
Jul 30, 2017 · 10 min read

A common question I’m asked by divers is how to improve their air consumption. While the simple answer is “breathe less”, or jokingly, “breathe in once before you descend, then breathe out slowly for an hour, and breathe in again when you finish the dive”, both are flippant.

There are many options / tools and methods available to help you dive longer. First, it helps to understand why you need to breathe, and how much you breathe.

Air contains about 78% nitrogen, 0.93% argon and 0.04% carbon dioxide, none of which is useful to us.

It also contains 20.95% oxygen — the important part — of which we burn about a quarter of (5%-6% of the 21%) with each breath fueling chemical reactions in our bodies. Our muscles and brain, in particular, consume a lot of oxygen to function.

Check your resting breathing rate

If possible, follow this procedure that tech and solo divers do to better understand themselves.
Grab a tank, a regulator, and your favourite tv show. Open the tank, sit down, watch an episode and check the pressure every 10 minutes. Ideally you should get a nice averaged resting breath rate after 30 minutes.
This gives you an idea of what you’re like when you’re not diving, to better understand if the issue relates to diving at all, or is just based on your own size and metabolism.

Size

Being simply larger means larger muscles. More oxygen is required to work them, even when resting. Body builders tend to use a lot more air than marathon runners, for example.

Height has a direct relationship to lung size. For men, lung size usually ranges between 3L and 5L. Height is not the only factor, it’s related specifically to trunk (chest/torso) height and radius. Women are smaller around, for the same height, than men, reducing their lung volume.

Bigger lungs mean a greater volume of air moved with each breath.
Unfortunately, not much can be done about this. While lung volume reduction surgery is a real thing, it’s usually only used in cases of severe emphysema.

…please don’t get LVRT in a dodgy Thai hospital.

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Core temperature

Your body burns energy to stay warm. The more insulation you have (fat or neoprene, discussed later), the less heat you lose to conduction, and the less hard your body has to work to stay warm.

Sex

Women tend to use less air than men, due to smaller frames, and thus smaller lungs. However, women also tend to feel the cold more easily than men, and tend to require more weight than men (which potentially means working harder).

Physics

If you find that you’re diving deeper “just because you can”, reconsider your dive profile. Go deep because there is something to see there, not just because you recently certified as a Deep Specialty Diver.

Each 10m of depth is another atmosphere of pressure, and another multiple of air consumption. That is, at 20m (3ATA), you’re using 50% more air per breath than at 10m (2ATA).

Use Nitrox

Okay, this entry was a bit tongue-in-cheek. There is a myth that because Nitrox is air enriched with additional oxygen, you don’t need to breath as much while on it, to get the oxygen you require.

There was a study done, which showed there IS in fact some truth to this. In the realm of 1%.

As in, if you’re getting only 30 minutes out of a tank, you might expect an additional 18 seconds on nitrox.

If you’re looking to use less air, nitrox is not the answer.

Fitness

The fitter you are, the lower your resting heart rate, and the quicker your heart rate comes back down after exertion. Emphasise cardio exercise in your daily life, not muscle bulk. Muscles require a lot of blood, and thus more breathing to power.

Carrying less fat (while insulating), will help streamline you (see below), and make it easier to move through the water. The more of you there is, the more work you will need to do to move around. Admittedly, if you are drift diving, or moving especially slowly, then being slender has a less dramatic effect on your air consumption.

Health

Don’t smoke, especially an hour or two before diving. Most people notice a marked improvement in air consumption within 3 months of quitting regular smoking.

Comfort

If you are cold, your body will be working harder to keep your core temperature up. When your heart rate is up, your metabolism is up, you will be burning more air to fuel this process.

Old, stretched, torn wetsuits do not insulate or retain water very well. Check for a working zipper and holes when getting rental gear.

So if you’re getting cold and uncomfortable, first, get a well fitting wetsuit and boots. Second, start using a full length suit. Third, consider a hood, or better yet, a vest with integrated hood, which will cover the neck. Fourth, consider gloves.

Please note that many places do not allow the wearing of gloves! (It is against Green Fins policy, as some people who wear gloves tend to touch and damage coral more often). Consider instead going for a thicker wetsuit, or a semi-dry suit, or even a dry suit.

Less neoprene will make it easier to move, which will reduce your air consumption as you work less.
If you have less on your limbs, such as in a “5/3” suit — 5mm on the chest and 3mm on the limbs — then you should find it easier to move around in. Or use a suit with more advanced materials, like super stretch neoprene. Layering can be effective as well. Find what works best for you, based on your comfort and the water you’re diving in.

Calm down

When you first enter the water, your body reacts in a very primitive, survival-based way. Your heart rate increases, your outer limb capillaries close, and your body works to protect your core temperature. So, when you first get into the water (from a giant stride or back roll — it matters less for shore entry), stop and relax at the surface for a moment.

Put your face in the water, breathing from your snorkel, allowing the water to trigger your mammalian diving reflex.

Calm and slow your breathing. Close your eyes a moment. Then open, give the okay, and descend.

Once you descend, and reach your desired depth, repeat. Calm and slow yourself. Then give the okay and enjoy your dive.

Breath control

Focus on your breathing. Notice it.
Take a yoga class. Zen. Consider a koan.

Practice slowing your exhalation. Two seconds in. Four seconds out. Three seconds breathing in. Six seconds slowly breathing out. Even up to four seconds in, and eight long seconds slowly breathing out.
Don’t stress about counting; the idea is to just breathe out slower than you are breathing in.

Pause. Never stop breathing — the number one rule in scuba diving — but pause. In between each inhalation and exhalation, pause for half a second. Don’t force the next breath, don’t hold it, but slow everything down.

Rest

In current, if you’re getting exhausted, or if you’ve just been startled by something (like a snake passing nearby), or a brief unexpected sprint (like running from a titan triggerfish) — stop.
Deploy a reef hook if the site allows for it. Hook in, and rest. Calm your breathing before trying to resume swimming.

Note: many resorts and areas ban reef hooks because of the damage they can do when deployed poorly.

Swimming

Practice all of the common (and some uncommon) kicking styles. Flutter and frog are the two most common.

A flutter is good for a strong, straight line.

Frog kick is great for efficiency in calm water.

A helicopter or reverse kick can save a lot of distance in maneuvering.

Modified flutter or frog is perfect for silty bottoms.

Different kick styles are often suited for different diving situations. The right kick can make all the difference to the effort expended.

A good swimming form will increase efficiency, reducing your work, reducing your air usage.

Changing kick styles will work different muscle groups, reducing fatigue and cramping as you switch between them, even if they aren’t the “best” for a situation.

Know when to not swim, and just hover or drift.

When drifting, learn to position yourself closer or further from the wall or floor to control your speed instead of swimming to do so.

Flailing

Every time you activate a muscle, it creates an oxygen demand until it relaxes. The less muscles you use, the less oxygen your body needs, and the less you need to breath.

If you kick using just your thighs and hips — not your calves, and not your arms — you minimize your muscle usage.

New divers frequently use their hands and arms to try and swim, which is rarely effective. It generates very little thrust, and activates a number of large muscle groups (such as the chest and shoulders). It can also put an unaware diver at a heightened risk of injury, from flailing into urchins, sea jellies, anemones and everything else.

Mastering the ability to hover, as taught in the Open Water/Scuba Diver course, is a great way to reduce this.

Trim, weights and buoyancy

Be in the correct trim (position) for the diving you’re doing. Face down, vertical, one side up… move your weights to help keep you in your preferred position for the dive you will be doing.

Do a weight check to ensure you’re properly weighted for the water (salt content), wetsuit and your current body size (Christmas/holiday gorging can affect your buoyancy, for example).

Lastly, do a fin pivot to help you become neutrally buoyant if you are having trouble hovering in the water column. Watch where you put your fin tips, but if you’re careful, it’s a good way to rest in a gentle current.

Streamline

Reduce drag in the water.

If you’re not overweighted, your BCD won’t be as full to compensate.

Take off anything you don’t immediately need all the time, especially big things like slates. Use pockets as much as you can. Don’t let things dangle. Anything you can do to keep your profile lean will make it easier to swim, which will reduce the amount of work you need to do, which will reduce your air consumption. Increasing your fitness will have a direct effect here.

Train

Take a Peak Performance Buoyancy Specialty course. All modern PADI instructors are able to provide training and certification in this three dive course over a single day.

This course will help improve your breathing, trim, buoyancy and kick styles.

How to compensate

If you have found you have done all you can reasonably do, but are still frustrated by shorter dives, there are a few options available.

Dive shallower

While this can sometimes be frustrating, physics supports this option. Ensure you have your own dive computer and have perfected your buoyancy, and then stay slightly higher than you would otherwise (unless otherwise directed by your Divemaster).

Remember, at 20m, you use air 50% faster than at 10m (3 atmospheres vs 2 atmospheres).

Bring more air with you

Bigger tanks

12 liter (11.5L or so for imperial sized) tanks are common and hold about 2400L of compressed air when filled to 200 bar.

Many dive shops stock larger 15L tanks for people just like you! These bigger tanks hold about 3000L of compressed air, and should get you an extra 25% more bottom time. A 30 minute dive becomes almost 40 minutes with the bigger tank, for example.

Bigger fills

In most places, a full tank is anywhere between 180 bar and 210 bar. However, yoke systems are usually safe up to 240–250 bar, and DIN systems up to 300 bar. That’s 50% more air, and more bottom time, with no change in equipment!

Some fillers regularly fill to 240–250 bar, which should be no problem, as long as equipment is well maintained and tested. Some of the issue comes from how much longer it takes to fill a tank with that much air.

If you find you need more, just ask the dive shop. Some places which normally fill to 180–200 will have tanks set aside with 220 bar. Or, can specially order / ask for a 240 bar tank. Diving with even 220 can mean the difference between splitting up a group, and being able to get in an hour long dive.

Be aware that this isn’t always for free! Some dive shops will charge a small fee for this extra service.

Go sidemount or twin-back mount

If you’re a sidemount diver, two “baby” tanks of 7L will hold 14L of air, and be easier to carry, move around with, and offer an extra 17% of bottom time, or so.

Two normal 12L tanks offer double the time, of course.

Double 15L tanks should be far more than any one recreational diver should need, holding 2.5x as much air as a normal single 12L diver carries.

Go Closed Circuit Rebreather (CCR)

If money and training are no object, check out closed circuit rebreathers (CCR). A rebreather recycles your air, scrubs the carbon dioxide and tops it up with more oxygen.

A normal tank of air so supplied should last at least 3 hours, maybe more.

Plus, there’s the advantage of no bubbles! Just quiet machine humming. The main disadvantages are the cost ($2,500AUD to $15,000AUD), the weight (especially for travel) and the maintenance. Not many dive shops are set up to support CCR either, so call ahead and plan appropriately if you go this route.

Conclusion

This doesn’t mean that the ideal diver is a tiny, slightly chubby Chinese long-distance female cyclist who is a yoga instructor on the side. However, it wouldn’t hurt.

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Diving Around Asia

Dive travel & underwater photography

Michael Fineberg

Written by

Diving Around Asia

Dive travel & underwater photography

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