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How Do SCUBA Tanks Work?

   November 6th, 2022   Posted In: Articles   Tags:

How Do SCUBA Tanks Work?

Curious about how SCUBA tanks work? The SCUBA tank, also known as a diving tank or diving cylinder, is what divers use to store and transport high-pressure gas to breathe underwater instead of needing to come up for air. It is called a SCUBA tank due to the SCUBA acronym, which stands for Self-Contained Underwater Breathing Apparatus.

The tank comprises two main parts to make it work: the pressure vessel and the cylinder valve. The pressure vessel is the large cylinder of the tank that is usually made of steel or aluminum. This is the container that holds the gas mixture the diver will breathe underwater.

The pressure vessel is then connected to the cylinder valve. Which is what is used to control gas flow to and from the pressure vessel. The cylinder valve also connects the SCUBA tank to the diving regulator, the mechanism from which you breathe.

What Type of Gas Is Inside a SCUBA Tank?

Now that we know a SCUBA tank is filled with a gas mixture to breathe let’s discuss exactly what type of gas it is. Most people would assume it is 100% oxygen the diver would be breathing in. But, there are several different gases to fill in your SCUBA tank.

Breathing pure oxygen past a certain diving depth can be toxic and even fatal to the diver! To avoid oxygen toxicity, gases inside a SCUBA tank can be mixed for a safe diving experience.

Here are a few of the most common gas mixes inside a SCUBA tank:

  • Air: A common mixture is standard atmospheric air for casual diving. This mixture is nitrogen, oxygen, and a small amount of trace gases. This mixture, however, is recommended for diving only up to 130 feet.
  • Nitrox: This mixture is also created with nitrogen and oxygen, but with more oxygen and less nitrogen than the air mixture. Due to the smaller amount of nitrogen, divers can be underwater for longer than if they use air in their SCUBA tank. Nitrox is a shallow-diving gas, not used on dives that exceed 95-112 feet.
  • Trimix: For dives that go beyond recreation, such as commercial and technical diving, there is Trimix which is comprised of nitrogen, oxygen, and helium. Unlike nitrogen and oxygen, helium doesn’t react in the diver’s body when going beyond a certain depth. With Trimix, divers can dive deeper without the worry of any potential oxygen and nitrogen side effects.
  • Heliox: Similar to Trimix, Heliox is also for commercial and technical diving, but this gas mixture only contains oxygen and helium—no nitrogen. This eliminates the possibility of any nitrogen-related complications and with a lower amount of oxygen, the primary gas is helium. A caveat with Heliox, however, is the diver may experience poor thermal insulation due to the lowering of body temperature over prolonged usage.

While there are plenty of options for what gas mixture to include in your SCUBA tank, always check what you are using before you dive so you know how deep, and long you can dive.

What is The Cylinder Valve?

Your SCUBA tank is filled with the appropriate gas mixture, now, how does the gas get to the diver? This is where the cylinder valve comes into play. The cylinder valve is attached to the top of the SCUBA tank. It controls the flow of gas from the tank by opening and closing of the valve. It is in charge of getting the gas mixture to the diver via the regulator or breathing apparatus. 

Once the gas travels from where it’s stored in the SCUBA tank to the cylinder valve and through the regulator, it reaches the diver for easy access to safely breathing underwater. 

Patrick Thomas is a Coast Guard veteran who grew up surfing and fishing in southwest Florida. Having lived in Puerto Rico and the Outer Banks, NC, he now works as a full-time photographer and author in Austin, TX. More of his work and photography is available at pkthomas.com.

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