Bulk tank regulator
A bulk tank regulator is used to regulate down the output pressure of bulk gas tanks, such as CO2 or scuba tanks. They are made in many different designs for use in welding, cutting, scuba diving, carbonization of beverages etc.
Some regulators regulate flow instead of or in addition to pressure, a pure flow regulator is not useful in most spudgun applications, since it doesn't drop the output pressure from the tank to a safe level.
A pressure regulator is ESSENTIAL when filling a PVC pipe chamber from a bulk tank to prevent a rupture. Also, an adequate pressure release valve should always be used in the event of a regulator seal failure.