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How Long Can My Tank’s Gas Supply Last on a Dive?

When you're underwater, the only thing keeping you going — besides the beautiful views — is the effectiveness of your scuba diving regulator and the air in your scuba tank. As the only way you can breathe underwater, knowing at least the basics about your scuba tank is important and can help ensure a safe and enjoyable experience while scuba diving.

One of the first things most scuba divers ask is how long their tank’s gas supply will last you on a dive. There isn't a one-size-fits-all answer, and knowing how a few important factors apply to you can help you narrow down the time limit on your dives.

How Long is the Average Dive?

In short, a good rule of thumb is that the average dive is about an hour, give or take a few minutes here or there. But those few minutes are not only important to your experience but can be the difference between a serious diving accident. The time limit is influenced by the size of your tank, the depth of your dive, and even any health problems you may have.

Dive Depth

Even as divers head lower and lower and enter increased pressure ranges, a quality regulator will keep your ease of breathing the same. However, that does not mean you shouldn’t be aware of your pressure readings. Pressure increases exponentially when diving, so even shallow divers should be aware of the distance at which they're diving. Pressure doubles and triples at 33 and 66 feet deep, respectively, so keep in mind the pressure readings of your pressure gauge.

Air Consumption Rate

Your air consumption rate (also known as surface air consumption rate) is important to determine how long you'll last underwater. Fitness, health, experience, buoyancy, and trim will all play roles in your gas consumption throughout the duration of the dive.

In addition, your levels of stress and your diving experience contribute to your air consumption rate. A new diver usually uses a decent amount of air when regulating their breathing, while a more experienced diver can conserve air and potentially extend the length of their dive.

Whether you're just starting your diving adventure or if you're an experienced diver, scuba diving training courses could be a great way to learn and improve your breathing. Regardless, it's good to keep in mind a few of these tips to help you improve your air consumption rate while underwater:

  • Stay calm and relaxed while breathing underwater.
  • Take deep inhales and exhales.
  • Move slowly.
  • Don't use your arms for swimming.

How Does My Tank Impact Dive Length?

A few factors differentiate tanks and scuba cylinders that can impact the air that flows through your dive regulators and, conversely, the length of your dive. Tanks come in all different shapes and sizes and carry different air pressures. Depending on the tank you choose, you might only be able to dive for a few minutes, or you could be diving for over an hour.

Tank Size

The most common size for a scuba cylinder is about 30-50 pounds and holds the equivalent of an 80 cubic foot steel tank of air compressed at 3000-3500 PSI. Tanks are available in all ranges and sizes and can be useful for varying dive lengths.

Air Pressure in Tank

The greater the air pressure in your tank, the more time you can spend underwater. But as your pressure gauge fluctuates, you want to keep in mind your decompression zone. The more high-pressure air you consume through your scuba regulators, the closer you get to suffering decompression sickness. Pay attention to your dive computers, and don't ignore any feelings of sickness or nausea.

Twin Tanks?

Twin tanks are a great way to extend the length of your dive without carrying much more weight than you normally would with your other dive equipment. An 80 cf tank is roughly the same weight as two 40 cf tanks and carries significantly more air. Consider using twin tanks if you are diving multiple times a day or want to dive for an extended period. 

Your Health Plays a Part

If you're suffering from lung-related problems, you might not be able to dive for an extended period, and you'll have to pay attention to your pressure measurements much closer than most. 

Smokers are one of the highest risk parties for diving-related issues. Smokers consume much more oxygen than most due to higher levels of carbon monoxide in the blood. Thus, some smokers may notice a pressure gauge that diminishes in half the time of any non-smoking divers.

Get All the Air You Need for Your Next Dive!

The amount of dive gas that needs to pass through your dive regulators depends on so many factors that you'll probably need a bit of assistance on your adventure. Fortunately for Philadelphia residents looking for professional training, Scubadelphia Diveseekers can help! Schedule an appointment today and dive right into the marine experience of your dreams.