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: You inhale, thereby lowering the pressure in the intermediate-pressure chamber to below the ambient water pressure. The water pressure pushes inward, opening the valve or piston. The open valve connects the high-pressure chamber with the intermediate pressure chamber. Air flows from the high-pressure chamber into the intermediate-pressure chamber, thereby increasing the pressure in the intermediate-pressure chamber. When the pressure in the intermediate-pressure chamber equals the ambient water pressure, the valve or piston closes. The process repeats when you inhale again. Operation of a regulator's first stage
The first stage usually has several ports with hoses that lead to the second stage as well as to other devices, such as an additional second stage, tank-pressure gauge and/or buoyancy control device (BCD -- more on this later). Inside a regulator's second stage
The regulator's second stage consists of: Plastic chamber with an outer rubber diaphragm that is in contact with ambient water pressure
Purge button
Inner valve that is connected to a movable lever
Exhaust valve
Mouthpiece
The second stage is connected by a hose to the intermediate-pressure chamber of the first stage. This is how the second stage operates: