aqualung

[romanu]

how does it work?

[SteveD]

SCUBA (Self-Contained Underwater Breathing Apparatus) is explained here:

http://entertainment.howstuffworks.com/scuba1.htm

[jake-the-peg]

An aqualung comprises of a high pressure air cylinder containing air at about 200 atmospheres pressure and a demand valve or regulator that reduces the pressure to the correct pressure at which you're diving

The demand valve has a first stage that attaches to the cylinder and that reduces the pressure by a first step and a second stage which takes it to the correct pressure.

The first stave is basically a needle valve - a needle goes into an opening and is balance by a spring.

The second stage has a diaphram with a lever. When you breath in the diaphram is sucked in and air is released into your mouth. When you breath out the air is expelled through the little mushroom valves (think rubber flaps)