The time that your scuba tank lasts depends on several factors: how long you have been diving, your level of exertion during the dive and what depth you are diving at.
Of course, time limits depend on the individual diver’s level of exertion and the depth at which you are diving. The rule is that during any dive, no matter where you are in the world, you cannot use your tank for more than 80 minutes. We have some other things to consider as well though. Let’s say your air consumption is 1/60 (20 cubic feet per minute), 2/60 (40 cubic feet per minute) or 3/60 (60 cubic feet per minute). You will enter the water with an 80 cubic foot scuba tank filled with air, which means your tank starts at 3000 PSI. When you first enter the water and before your descent, you will typically burn around 1500 PSI of air. Let’s take two scenarios and go through them here:
Time limits
It is important to note that time limits depend on the individual diver’s level of exertion and the depth at which you are diving. Your air consumption rate, type of diving, and water temperature all contribute to how long your tank will last.
You cannot use your tank for more than 80 minutes
The rule is that during any dive, no matter where you are in the world, you cannot use your tank for more than 80 minutes.
In general, a scuba tank will last for approximately 80 minutes of air when you’re diving. The rule is that during any dive, no matter where you are in the world, you cannot use your tank for more than 80 minutes.
However, this does not mean that after 80 minutes on one tank you need to switch to another one. This is because most people do not actually spend all of their time underwater at the maximum depth of their dive; instead they spend most of it at shallower depths where there is less pressure and thus less oxygen required by the diver’s body (this means he/she uses less oxygen).
Other things to consider as well
But we have to consider a few other factors as well. The amount of air consumed depends on the depth and exertion level, as well as your fitness level and age.
If you’re diving at 20 feet with no exertion, you might use up just over half your tank in an hour. However, if you’re doing some deep water exploration or spearfishing for an hour at the same depth, it’s highly likely that you’ll use up all the air in that tank during that time period.
Air consumptions
Let’s say your air consumption is 1/60 (20 cubic feet per minute), 2/60 (40 cubic feet per minute) or 3/60 (60 cubic feet per minute). If you’re a moderate swimmer, the average air consumption rate for offshore divers is about 1.5 to 2 standard atmospheres per hour. An average recreational diver might use about 12 to 18 liters of oxygen in an hour, while an experienced scuba diver can consume up to 30 liters of oxygen in one hour.
Scuba tank starts at 3000 PSI
Your tank will be filled with air at 3000 PSI. It’s an 80-cubic-foot tank, which means that there are 80 cubic feet of air inside your scuba diving regulator.
The first thing you need to understand is that the initial pressure in your scuba diving regulator is 3000 psi (pounds per square inch). This means that when you take a breath from your tank, you’re breathing out air at 3000 psi pressure.
When you first enter the water you will typically burn around 1500 PSI of air
The first thing to know is how much air you burn when you first enter the water and before your descent. This amount of air is referred to as the “surface interval,” which can be calculated by taking the total number of minutes your dive lasts and dividing it by 15. For example, if your dive lasts for 60 minutes, multiply 60 by 15, bringing you to 900 PSI.
If you are diving with another person (or persons), make sure that each person has enough reserve gas for their surface interval to avoid running out of breathable air at any point during their dive. Once this has been taken care of, it’s time for those experienced divers among us:
Let’s take two scenarios and go through them here
Scuba divers use air to breathe underwater. The average recreational diver consumes about 22 liters of air per dive, but this will vary depending on the depth of the dive and how much exertion is involved in the dive.
Technical divers are those who specialize in advanced diving techniques that require special training and equipment. These divers consume more air than recreational divers do on average because they tend to dive deeper and longer than recreational divers do.
In most cases, you should not plan your dive based on how long your tank will last; instead, you should plan it based on how much time you think it will take for you to complete your planned activities at each depth—a concept called bottom time (BT). You can calculate BT by taking into account factors such as visibility/water quality, current strength/directionality/swiftness (TSI), distance traveled between depths or points along a line trace route (LTR), number of stops during LTR line tracing depending on TSI conditions (one stop every 10 feet if possible)
At 100 feet down
When you reach 100 feet down, a typical recreational diver’s air consumption rate can double or even triple from what they experience while gently kicking at 20 feet below the surface. The reason for this is that when you are diving deep, your body is working harder to stay warm. As a result, more oxygen is required to keep up with your body’s needs.
In this case, our recreational diver would have approximately 6 minutes at depth until their air reaches 500 PSI and they need to ascend up to a shallower depth to get back to 1000 PSI.
We can see that a recreational diver who is diving to a maximum depth of 100 feet will have approximately 6 minutes at that depth before they need to ascend in order to get back up to 1000 PSI.
In this case, our recreational diver would have approximately 6 minutes at depth until their air reaches 500 PSI and they need to ascend up to a shallower depth to get back to 1000 PSI.
Conclusion
In this case, our recreational diver would have approximately 6 minutes at depth until their air reaches 500 PSI and they need to ascend up to a shallower depth to get back to 1000 PSI.