Which stage reduces tank pressure to intermediate pressure?

• A. The first stage
• B. The second stage
• C. The third stage
• D. The fourth stage

Answer: (A)

Gas must be reduced from the tank’s very high pressure to a breathable level in stages. The first stage attaches directly to the tank and lowers that high tank pressure to an intermediate pressure (typically about 9–11 bar above ambient, roughly 130–160 psi above the surrounding pressure). The second stage then takes that intermediate pressure and further reduces it to ambient pressure as you inhale. Because of this setup, the stage that brings tank pressure down to intermediate pressure is the first stage. The second stage doesn’t directly touch tank pressure; it uses the intermediate pressure to deliver gas at ambient pressure. Third and fourth stages aren’t part of a standard recreational regulator, so they aren’t what reduces tank pressure to intermediate.