Do you want to learn how to calculate compressed air consumption?
Have you moved beyond scuba diving basics and plan to start on your own as an independent diver?
If your answer is yes, you should definitely know your Surface Air Consumption or SAC.
Why? Because it can save your life.
As we all know, we use more air on a deeper dive rather than on a shallow dive.
Probably, that is because the air that we breathe is denser on a deeper dive. So, we take in more gas atoms with each breath.
Generally, because of Boyle’s Law, we know how many times the air is denser at different depths.
Here, I will share with you how to calculate your compressed Air Consumption.
Steps on How to Calculate Compressed Air Consumption
Learned Your Air Consumption (SAC)
Surface Air Consumption is a statement of your air consumption during diving, with the diver’s profundity removed from the condition.
As we as a whole know, according to Boyle’s Law, air consumption increases with depth due to the pressure increases the density but reduces the volume of the air we breathe.
Simply looking at your manometer will not just tell you how much air consumption do you consume.
When you know your air consumption (SAC), you can make your estimations about how much air you will probably use during a dive to any given depth. It will allow you to factor air consumption into your diving courses.
Do Some Measuring
To begin with, do various dives at various depths and conditions. For every one of these dives, note down the time, gas utilized, cylinder size, and depth.
In a perfect world, incorporate a dive where you were truly stressed because of flows, or swim for 5 minutes at most extreme exertion during a dive.
At that point, in that 5 minutes, make a note of the air consumed, so you can have the idea about your air consumption while working under strain.
Do the Math
When you have these numbers, you can begin your computations. While there are various web locales where you can basically punch the numbers into boxes and find a solution,
I think that it’s helpful to have the option to do the estimations yourself.
Two Types of Calculations for Air Consumption
The calculations go as follows:
SAC = (VT x VC) / ((T x P)
- SAC is the air consumption.
- VT is the Total Volume of the cylinder used in liters.
- VC is Consumed Volume in bars during the dive.
- T is the duration of the dive.
- P is the pressure in bars of the average depth of the dive (or maximum depth if you stayed at the same depth the entire dive)
For the imperial system, the formula gets a little trickier but still easy once you grasp it. It goes as follows:
R x PSIC / W / T / P
- R is the cylinder rating in cubic feet.
- PSIC is the Psi consumed.
- WP is for Working Pressure, which is the rated pressure that the tank operates under.
- T is the time in minutes.
- P is the pressure at the average depth of the dive, or maximum if you’ve stayed at the same depth the entire dive.
A diver uses 5 Bar per minute at 15 meters of seawater. How much do you think the diver will use at 22 meters of seawater?
First, bring the diver to the surface and think that like a balloon. Then you will find out if how many bars per minute the diver will breathe there.
To do this, you need to know the pressure at 50 meters of seawater.
Meaning, it is 2.5 Bar 15 divided by 10 plus 1. The diver will use 2.5 times less air at the surface.
5 Bar P/M / 2.5 = 2 Bar P/M. The diver will use the 2 bar per minute at the surface.
Now, we can take the diver to the second depth of 22 meters of seawater. The pressure at 22 meters of seawater is 3.2 bar 22 divided by 10 plus 1.
The diver will use 3.2 bar more air per minute and at the surface.
2 Bar P/M x 3.2 = 6.4 Bar P/M.
Probably, the diver will use 6.4 Bar P/M at 22 meters of seawater.
At the 30 meters of the seawater, where the pressure is 4 bar at the air, your breath is 4 times as dense. So, you breathe in 4 times as much air as you would do at the surface.
Let’s make it simple. A diver uses 2 bars of air per minute at the surface.
How many bars per minute do you think the diver will use at 25 meters of the seawater?
First, we know that the diver will use more than 2 bar per minute, not less, so we need to multiply the diver air consumption at the surface.
The pressure at 25 meters of seawater is 3.5 bar, 25 / 10 + 1.
The diver will use 3.5 times more air at 25 meters two bar.
2 Bar P/ M x 3. 5 = 7 Bar P/M.
So, here you will use the 7 bar per minute at 25 meters of seawater.
If the diver is diving in the freshwater, the diver will slightly use less air than in the seawater because the pressure is slightly less.
The pressure at 25 meters of fresh water is 3.43 Bar.
25 meters divided by 10.3 plus 1. 25 MFW / 10.3 + 1.
So, the diver will use 3.43 times more air than the 3.5 times more air the diver will use in the seawater.
2 Bar P / M x 3.43 = 6.86 Bar P / M.
So, the diver will use the 6.86 Bar P / M at 25 meters of freshwater.
The diver will use 7 Bar per minute in the seawater, meaning there is no much difference.
Variables That Affect Air Usage
Air consumption is an individual issue. If two divers sit onshore breathing from a similar brand of the controller and equivalent size, similarly filled scuba chambers, following a couple of moments, both will have decreased the weight staying in their tanks. Yet, one will have utilized more air than the other. Indeed, even out-of-the-water jumpers use air at varying rates.
The measure of air utilized starts with the diver’s size and physical molding. As a rule, a bigger jumper is probably going to expend more air than a little diver. Physical wellness is likewise a factor. A diver who is in acceptable vigorous condition ordinarily utilizes less air than somebody who doesn’t practice routinely.
When you enter the water, there are significantly more factors that influence air utilization. Here’s a review of the physical science exercise you got during your lessons in your scuba certification.
Surrounding pressure increments by 1 climate (ATM) for every 33 feet (10 m) of expanded profundity, bringing about changes to the weight/volume/thickness of a diver’s air supply. At 33 feet (10 m) (2 ATM), the surrounding pressure is twofold what it is at the surface; at 66 feet (18 m) (3 ATM), it’s multiple times more prominent than at the surface.
Thus, at a profundity of 33 feet, you will expend twice as a lot of air as you do superficially.
At 66 feet (18 m), threefold the amount of when sitting on the shore breathing from the regulator. In this way, the deeper we dive, the more air we consume.
Ways to Improve Air Consumption
Air consumption improves with understanding. I have not known another diver whose air utilization didn’t improve as he turned out to be progressively agreeable in the water or potentially through diving strategy changes.
Wearing the proper measure of weight, which implies diminishing the measure of weight you wear, is an initial step to improving air utilization.
An appropriately weighted diver has a trim, evenly situated situation in the water section.
A corner to corner direction, where the head and upper-middle are higher than the legs, makes you crash through the water instead of floating.
If you’re not an experienced diver, then one of the first things you’ll need to learn about is how to pick the best scuba tank.
To turn out to be impartially light, an overweight diver must add overabundance air to the BC. This floats the chest area and makes furrowing substantially more truly requesting. Weight yourself appropriately by leading a weighting test each time you change hardware or move among salt and crisp water, and your air consumption will improve.
Another slam dunk that any diver can do to improve air consumption.
Streamlining diminishes drag, which is the opposition experienced as you travel through the water. The more prominent your drag, the more exertion you’ll use. Expanded exertion implies expanded air requests, and there goes your air utilization.
It starts with making sure about all frill gear near your body. Affix up your check support and octopus. Spot your record inside a lightness compensator pocket. The objective is to cause your underwater profile to take after a dolphin smooth and smooth with insignificant drag.
Next, center around your swimming procedure. To get streamlined, appear as a torpedo. Become smooth and smooth, with your head, middle, legs, and blades on a similar flat plane. Arms at your sides or collapsed over the middle. Blade with moderate, conscious movements.
Utilizing the best possible gear for nature will help you maintain a strategic distance from rapidly sucking down your air supply. Cold diver utilizes more air because their bodies need to work more earnestly to keep up the center temperature. Wearing the best possible warm assurance will keep you warm and broaden your air supply.
Move gradually and unwind.
Vitality proficient diver slice through the water gradually, utilize a productive kick, and inhale long, slow, and loosened up breaths. Each development is intentional and intended to create impetus utilizing the least exertion. Hold fast to the arranged profile and go no more profound than is fundamental.
Vitality effective divers don’t continually modify their gear and clear the veil. Once impartially light at the arranged plunging profundity, use lung volume varieties to keep your profundity consistent.
If you should rise a couple of feet to ignore a block, take two or three more profound breaths. At that point, inhale marginally shallower for a minute or two to come back to the first plunging profundity.
Loosening up underwater is an air preservation strategy that is more difficult than one might expect. The more agreeable you are at profundity, the less air you use. Think positive musings, slow down, inhale gradually and breathe out completely; make the most of each development, and before you know it, you’ll start to unwind, and your air supply will last more and more.
Check out PADI for some of their courses about Air Management.
Air Consumption Terms to Remember
Surface Consumption Rate (SCR)
The air a diver uses at the surface, expressed in psi per minute.
Depth consumption rate (DCR)
The air a diver uses at a specific depth, expressed in psi per minute.
Estimated Depth Consumption Rate (EDCR)
An estimate of the air a diver will use at a specific depth, expressed in psi per minute.
Estimated Air Time EAT
The estimated amount of time a diver’s air supply will last at a specific depth, expressed in minutes, based on psi/ minute or cubic feet/minute.
Cubic Feet Per Minute (CFM)
The cubic feet of air a diver uses in one minute.
Estimated Cubic Feet Per Minute (ECFM)
An estimate of the cubic feet of air a diver will use per minute at a specific depth.
Remaining Air Time (RAT)
A figure calculated and displayed real-time by most air-integrated dive computers.
Knowing your rate of air consumption is very important for planning dives.
However, some calculators’ equation will 100% comes out wrong as if it matters for the calculator to know what are you dividing on first.
Basically, learning how to compute your air consumption properly will be a good idea.
So, now if I’ll ask you how your air consumption is? What would be your answer?
Is it “Pretty Good?” “Not bad.” “I don’t know.”