Re: How does an aqua lung work?

There are many types of aqua lungs. These are general statements about how two systems work that are used for scuba diving.

Open-circuit - this system is a scuba regulator. It is used by most recreational scuba divers. The regulator attaches to a scuba tank that is filled with compressed air. The first stage of the regulator steps down the pressure in the tank (about 3000 psi) to an intermediate pressure (about 130 psi). The second stage of the regulator goes into the mouth of a scuba diver. It steps the pressure down to ambient pressure. That is, the same pressure as the surrounding water.

Closed-circuit - this system is a re-breather. In a fully closed-circuit re-breather, the air that a diver exhales is filtered using soda lime. This removes the excess waste gas (carbon dioxide). After that, small amounts of oxygen are added to supplement the remaining gas supply that the diver breathes.