How many liters of air is contained in the O2 bottle when filled to capacity?

• A. 500 liters
• B. 410 liters
• C. 300 liters
• D. 450 liters

Answer: (B)

When a bottle holds compressed gas, the amount of gas available at surface conditions scales with how hard it’s pressurized. The liters of gas you can get out at ambient pressure is basically the bottle’s physical volume multiplied by the fill pressure, then divided by atmospheric pressure. In practice, use the approximate atmospheric pressure of 14.7 psi.

So, if the oxygen bottle has a small nominal volume (for example 3 liters) and is filled to about 2,000 psi, the total liters of gas at surface conditions would be about 3 × (2000 / 14.7) ≈ 410 liters. Temperature changes are a minor factor here, but this is the core way to estimate how much gas is stored in a pressurized cylinder.

If you change the bottle size or the fill pressure, the liters of gas change accordingly, which is why different numbers would correspond to different combinations of volume and pressure.