Which stage of the regulator reduces working tank pressure to intermediate pressure?

The first stage of a scuba regulator is responsible for reducing the high-pressure air from the tank to an intermediate pressure that is suitable for the second stage to deliver air to the diver. This stage connects directly to the tank valve and utilizes various mechanisms, such as a diaphragm or piston, to accomplish the pressure reduction. By converting the high-pressure air (often around 3000 psi or more) to a much lower, manageable level (usually around 140-160 psi), the first stage ensures a safe and consistent flow of air regardless of the diver’s depth or tank pressure.

The second stage, on the other hand, is designed to further regulate this intermediate pressure air to a breathable pressure, corresponding to the diver’s environment. There is no recognized third stage or intermediate stage in standard regulator designs; these terms do not refer to stages that perform this specific function of pressure reduction. Thus, the first stage is definitively identified as the component that reduces working tank pressure to intermediate pressure, making it the correct answer.