Attach the regulator. If the regulator's out of reach, lay the tank and BCD down, with the BCD up, before you go get it.The tank valve opening may be covered by a piece of tape or a plastic cap. If so, remove the tape or cap (discard tape properly - please do not litter).Check the valve opening for an O-ring (yoke system - for DIN, check the regulator first stage connection). It should be clean and free from cuts or nicks. If you need a new O-ring, see your instructor.

Open the tank valve slowly - just for a burst - to blow any accumulated water or dirt from the valve opening. Aim it away from people. If you're certain there's no water or debris, you can skip this step.Remove the regulator dust cap by loosening the yoke screw (yoke system) or unscrewing (DIN system).With the tank between your legs and the BCD away from you, put the first stage on the tank valve so that the valve opening meets the first stage opening, and so the second stage hose leads to the right. The primary second stage hose goes over your right shoulder.

Tighten the yoke screw until it is just finger tight, or for DIN equipment, gently screw in the regulator until it is snug.
Attach the low pressure hose from the regulator to the BCD low-pressure the working pressure on the tank and compare it to theSPG, and you'll have an idea how full the tank is. You'll quickly learn the full pressure for most tanks in your areCheck your air with the submersible pressure gauge.

Turn on the air and check its operation. You should now be ready to turn on the air. Hold the SPG in your left hand away from you, facing away, as you turn it on - this is a precaution in the unlikely event the SPG leaks internally and the face bursts; modern SPGs have blow out plugs so this isn't likely to happen even if it does have a leak. Play it safe anyway