CHAPTER 7 Scuba Air Diving Operations
Figure 7-1. Schematic of Demand Regulator.
First Stage. High pressure air flows through the orifice of the first stage into the intermediate chamber. When the pressure in the
intermediate chamber reaches ambient plus diaphragm balance spring set pressure, the first stage assembly closes.
Second Stage. Upon inhalation the second stage diaphragm moves inward and the horseshoe lever opens the second stage valve
assembly. Intermediate pressure air from the hoses is throttled across the orifice and fills the low pressure chamber to ambient pressure and
flow is provided to the diver. Upon exhalation the diaphragm is pushed outward and the second stage in closed. Expired air is dumped from
the low pressure chamber to the surrounding water through the exhaust valve.