Despite the number of manufacturers of SCUBA regulators, each with multiple models, open-circuit regulators still follow the same general design used for decades. An open-circuit SCUBA regulator provides on-demand breathing gas to a diver through two stages: a 1st stage regulator attached to the pillar valve of the SCUBA tank, and a 2nd stage regulator through which the diver breathes.
1st Stage Regulator
The 1st stage regulator attaches to the pillar valve through an O-ring seal. Yoke valves allow the regulator to be attached using a yoke and a screw to secure the regulator. DIN valves allow the regulator to be threaded into the pillar valve. The 1st stage regulator consists of two pressure chambers: a high pressure chamber and an intermediate pressure chamber.
The intermediate pressure chamber uses ambient water pressure to regulate the flow of gas from the high pressure chamber (connected to the pillar valve) to the intermediate pressure chamber. As the pressure in the intermediate chamber drops below the ambient water pressure, a valve or piston is opened, allowing the air to flow from the high pressure chamber to the intermediate pressure chamber. When the pressure in the intermediate chamber and the high pressure chamber equalize, the valve or piston closes.
High Pressure Hose
The 1st and 2nd stage regulators are connected by a high pressure hose that allows the gas from the 1st stage regulator to pass to the 2nd stage regulator. Additional high pressure hoses are usually attached to the 1st stage regulator that connect to the pressure gauge, buoyancy compensator and octopus regulator.
2nd Stage Regulator
The 2nd stage regulator connects the hose from the 1st stage regulator to the diver's mouth. When a diver inhales, a diaphragm made of rubber or silicone opens a lever allowing breathing gas into the regulator. This gas passes through the mouthpiece of the regulator into the diver.
When the diver exhales, the diaphragm contorts outward, allowing the lever to close the gas supply from the 1st stage regulator. The increased pressure in the 2nd stage regulator opens an exhaust valve, allowing the exhaled gas to escape out of the regulator. Ambient water pressure closes the exhaust valve, and the process repeats with each breath.
Article Written By David Chandler
David Chandler has been a freelance writer since 2006 whose work has appeared in various print and online publications. A former reconnaissance Marine, he is an active hiker, diver, kayaker, sailor and angler. He has traveled extensively and holds a bachelor's degree from the University of South Florida where he was educated in international studies and microbiology.