Your regulator makes it possible to use the air in your tank. It reduces the scuba tank's higY; pressure air to match the surrounding water pressure, and it delivers air only on demand, when you inhale. It regulates the air flow, hence the name "regulator." 'I"echnieallv. it's a highly sophisti-cated demand valve, so in some areas divers prefer "demand valve" to "regulator."

Styles and Features. The moderi scuba regulator is a simple and reliable device with only a few moving parts. It has two stages: a first stage, which vou attach to the scuba tank valve and a second stage that has a mouthpiece. The stages reduce high-pressure air from the cuba rank frequentially.

The first stage reduces the high tank presure to an intermediate pres-sure of 7-10 bar/100 to 150 psi above the surrounding water pressure. The second stage recdct-s this intermediate pres-sure to the water pressure surrounding you, which is what you need for comfortable breathing. Easy breathing is the most important feature of a regulator.

Regardless of make, all modern regulators share a relatively similar basic structure. Fermiliarization with regulator termi-nology and how it functions will help you understand further explanations regarding regulators.Look at the regulator second stage diagram. The second stage is haically a cup or air space covered with a flexible diaphragm (usually silicone rubber), a lever-operated inlet valve, a mouthpiece and an exhaust valve. When you inhale, you pull the diaphragm imvard, which pushes the inlet valve lever to air. When you stop inhaling, air pressure inside the second stage rises, and the diaphragm return,, to it relaxed position, releasing the lever and allowing the valve to close. The purge button lets you manually control the floA° of air by depressing the uiaphrasm and valv lever.

When you exhale. the exhaust valve opens and the air vents out through the one-way exhaust valve. The exhaust valve remains closed when \ once not exhaling, keeping water out of the regulator.