A regulator is designed to reduce the high pressure air of the rank to a level that is usable. It delivers air to the diver only when the diver inhales.

The modern scuba regulator is a very simple and reliable device with only a few moving parts. They have two stages: a first stage that attaches to the scuba tank and a second stage that has a mouthpiece. High-pressure sir from the scuba tank is reduced sequentially in each stage. The first stage reduces the high tank pressure to an intermediate pressure of 100 to 150 psi above the surrounding water pressure. The second stage reduces the intermediate pressure to that needed for comfortable breathing. Easy breathing is the most important feature of a regulator.

Regardless of make, all modern regulators are relatively similar in basic structure. Becoming familiar with regulator terminology and how it functions will help you understand the mechanics of how they work. You will learn more about this in you certification class.

When choosing a regulator the singe most important feature is ease of breathing both inhaling and exhaling. Choose an easy breathing regulator by comparing flow rates and breathing resistance.

This information was obtained from the Padi Open Water Diver Manual