How to improve your air consumption while diving
Table of Contents
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If you recently started scuba diving, you might have noticed something: on a dive someone will usually come out of the water with significantly less gas left in their tank than the others. Maybe that person is you! It's completely normal for new divers to use more air than experienced ones; there are a multitude of factors influencing their air consumption. However, in a diving group, the whole group has to stick together and base their organization on the diver with the highest air consumption. For this reason, it is a good practice to try to actively improve, to not be a limiting factor for the whole group.
Before continuing in this article, there is a very important point to mention: at no point should you hold your breath. You can have a slow and relaxed breathing rhythm as I'll talk about in more detail later, but it doesn't mean skipping/holding your breath, as we always want to make sure to follow the first rule of diving: never hold your breath.
Everyone has different air requirements. This is based on multiple factors such as gender, height, weight, fitness level, etc... You can only try so much to reduce external factors to reduce your air consumption
Tips for better air consumption
As much as air consumption can come from a variety of factors, some are actually under our control. I want to go over those that you can control, either before or during the dive and that will significantly improve your air consumption.
Finding your proper weight
A good diver knows how much weight they need to be comfortable. As new divers struggle to go down with few weights, their instinct might just be to use as many as possible, their thought process being that more weights equals an easier time getting down. However, as much as it is going to be easy getting down, once down there, the excessive weighting is going to make your dive exponentially harder.
First of all, more weight on yourself means more mass to move through the water. That is simply going to increase the required work for you and make you breathe more (increasing your air consumption). Think of it as hiking: hiking with only a light bag is going to be much easier than hiking with a stuffed bag that weighs a ton more. Something else to keep in mind is that you'll have to carry all the weight you have on yourself when you're on the surface; if there is a long walk to the dive spot, you don't want to be out of breath when the dive starts.
The other main reason being weighted properly is so important leads us to the next tip: Being improperly weighted can mess up your buoyancy, which will also lead to increased air consumption!
Keep in mind that a multitude of factors can influence your weight requirement: the type of water you are diving in, suit used, other equipment (such as BCD vs wing with a steel backplate), etc...
Improving you Buoyancy
Making sure your buoyancy is on point is one of the key points of diving: on top of improving your whole diving experience, it can actually improve your air consumption. How? Multiple ways:
- If you have an improper buoyancy, you are going to sink/float, and subconsciously (or even consciously), your body is going to try and compensate for that, meaning you're going to try to find your way back up to the proper depth, or force-finning yourself down, which obviously isn't ideal, and adds unnecessary exertion, which will lead to increased air consumption.
- Excessive inflating: if you always have to adjust the air in your BCD/wing, the air usage adds up in a long dive.
Improving your trim
Trim refers to the position of your body in the water. Meaning: are you horizontal? Vertical? Or something in between?
Trim is very tightly linked to buoyancy: if you are too vertical in the water, trying to move forward will inadvertently make you shallow up as well (as if you were kicking to go to the surface). Having a proper trim is key to improving your air consumption.
The ideal position in the water is to be as horizontal as possible. Some people, while trying to achieve a perfect trim, go over the top and angle themselves towards the depth, gaining depth with each fin kick.
Reducing excessive movements underwater
This comes down to limiting your exertion level. Simply put, the more you move and fidget around, the higher your air consumption will be. Keep in mind that every effort you make underwater is amplified and requires more energy than if it was on the surface. Diving is supposed to be relaxing, and on top of improving air consumption, it will reduce risks of hypercapnia (CO2 buildup).
If you were ever swimming against a current for an extended period of time, you'll realize that your pressure drops way faster.
Being more relaxed underwater pretty much comes down from mastering the two previous points: buoyancy and trim.
Breathing in a relaxed manner
Your breathing technique is largely going to contribute to good or bad air consumption. On top of making the dive longer, it will make the dive more relaxed and enjoyable.
There are multiple ways to "breathe correctly", but the main points are: slow, relaxed, and deep breathing.
A little trick to "extend" your breaths is to inhale slowly and deeply over the course of 3 seconds, then exhale over another 3 seconds. You can even extend that over a longer period, the important point is that you should fill your lungs completely and empty them completely during each breath cycle: that prevents any carbon dioxide buildup and helps you stay more relaxed.
As I mentioned at the beginning of the article: at no point should you hold your breath, taking deep, long, and relaxed breaths is fine, but skipping breaths should be avoided!
Using a properly maintained and serviced regulator
In the first stage and second stage of the regulator, there are some soft components such as O-rings that can get used up over time. If those aren't properly serviced and fail during a dive, it could lead to further problems.
Regarding air consumption and comfortable breathing, when servicing a regulator, technicians are also going to look at and calibrate two things:
- the intermediate pressure in the first stage.
- the cracking effort in the second stage: it basically measures how strong your inhalation has to be to start a breathing cycle in the regulator.
Both are crucial for breathing comfortably: if the intermediate pressure in the first stage is too low or if the cracking pressure is too high, it's going to require more effort to breathe. If the cracking effort is too low, your second stage will free-flow more often, and if the intermediate pressure is too high, it may damage your regulator.
Making sure those two values are well-adjusted can play quite a big part in improving your air consumption.
Getting more experience
Most of the previous tips can be summed into this one: to get better at anything, you need time and practice. This is the same for every aspect of diving, and as it was explained in this article, good air consumption is a combination of mastering multiple skills underwater.
If you want to become better, go out on more dives and try to actively improve the things listed in this article. If you want to make it easier for yourself, I suggest focusing on of of these at a time: take some time to figure out exactly how much weight you need, then take some more dives to dial in your buoyancy, etc...
Remember that improving takes time, and you might not see any significant change the first few times, but eventually, small changes over time will make you a significantly better diver.
SAC rate
SAC stands for surface air consumption. Because divers go to multiple depths, they want to know what their "base" air consumption is, simply put, how much air they breathe on the surface. The SAC rate describes how much volume of gas we breathe per unit of time. It is expressed in Liters per minute in the metric system and PSI per minute in the imperial system
How to calculate my SAC rate?
Metric system
The formula for Surface Air Consumption rate in the metric system is:
SAC = (used pressure x cylinder volume/time) x 10/(depth+10)
used pressure is expressed in bar
cylinder volume is expressed in Liter
depth is expressed in feet
Imperial system
The formula for Surface Air Consumption rate in the imperial system is:
imperial: SAC = (used pressure x cylinder volume/time) x 33/(depth+33)
Used pressure is in PSI
Cylinder volume is used in liters (although it can also be used in Cubic feet, the SAC rate will then be expressed in Cubic feet per minute, instead of liters per minute)
Depth is expressed in feet
Calculating your sac rate is quite straightforward, but you do have to get some information for it: First, choose a depth during which you'll stay for a certain amount of time. Then, record how much pressure you used during that set time, after that, you'll be able to calculate your SAC rate.
Here is an example: you use a 12L tank to go to a depth of 10 meters for 20 minutes. At the beginning of those 20 minutes you had a pressure of 200 bar, and after the 20 minutes, you have 150 bar. (in imperial units, that is a depth of 33 feet, 2900 PSI at the start, and 2175 PSI at the end)
Now you can calculate: SAC = ((200 bar - 150 bar) x 12L / 20 minutes) x 10/(10m +10) = 15 Liters/minute
Usually, when divers want to know how much gas they are going to use, they multiply their SAC rate by a factor (eg 1.2, 1.3, 1.4, etc... depending on the expected difficulty of the dive) to increase their safety margin.