Title: How Scuba Works | HowStuffWorks
Headings: How Scuba Works
How Scuba Works
Wet Suits, Dry Suits, and Buoyancy Control
Scuba Breathing Apparatus
Diving Physics, Physiology and Hazards
Effects of Scuba Diving on the Body
Scuba: Additional Equipment
Scuba Training
Amateur levels

Content: It reduces the pressure from the tank to a safe level for you to inhale, and it supplies air on-demand. To accomplish these tasks, regulators have two stages: First stage - The first stage attaches to the cylinder. It reduces the pressure from the tank (3000 psi or 204 ATM) to an intermediate pressure (140 psi or 9.5 ATM). Second stage - The second stage is connected to the first stage by a hose. It reduces the pressure from the intermediate pressure to ambient water pressure (such as 1 to 5 ATM depending upon depth). The second stage also supplies air, either only when you inhale (typical operation) or continuously (emergency operation). The first stage consists of high-pressure and intermediate-pressure chambers, separated from each other by either a valve-diaphragm combination or a piston, which is in contact with the ambient water pressure. The high-pressure chamber receives air directly from the cylinder, while the intermediate-pressure chamber is in contact with the ambient water pressure through the diaphragm or piston. The system operates like this: