All models of the Interspiro full face masks pretty much function the same. The first step is to attach an AGA HSA-2 supply hose to one of your low pressure ports located on your first stage regulator. Preferably one which will allow the hose to come over your left shoulder. Ensure that your first stage is putting out around 149 psi over bottom pressure. The AGA 2nd stage can work down to 90 and up to around 170 psi but 149 seems to be best. The hose then mates to the AGA's built in 2nd stage. This connection should be hand tight only. If you are using a positive pressure 2nd stage regulator, ensure the black lever located on the one the inner side of the exhalation part of the regulator is depressed. This lever will not be present on non-positive pressure 2nd stages. Located on the inside of the ffm is a nose clearing device. It has three adjustments which lower or raise the device. A correct setting would be when you push up on the front of the AGA ffm, the device covers your nose and you can equalize. If it is pushing on your nose or to far, it is out of adjustment (lower or raise as needed). Turn on the air. Listen for leaks, none should be present. If air escapes with a loud roar, the positive pressure lever is most likely not depressed. Don the ffm by first ensuring all straps are at the furthest out adjustment points. Put your chin in first then pull the head harness over your head. Position the pad over the crown area of your head. Start adjusting by pulling the two lower straps back toward the back of your head. Next go to the two straps near the temple area and do the same, pulling straight back. All four of this adjustments should be firm. The last adjustment will be the head strap. Pull it back as well but just enough to feel some pressure. Do not pull the straps outward when adjusting, this puts undo pressure on the straps causing them to bind and they can break off as they become older. If the mask is a positive pressure mask, on your first breath, the positive pressure black lever talked about earlier will pop to the open position pressuring up the inside of the mask. It will keep approximately a 1" water column over bottom pressure in the mask. If the mask is sealed properly, no air should leak out. Further, the 2nd stage will only give you gas when you demand it. It is not a free flow ffm! If you crack the seal while diving, the ffm will off gas. This is a safety pressure which all divers like. The positive pressure ffm has a little more safety pressure then the non-positive pressure ffm. However, reports from the field from users are that the non-positive pressure ffm fits more faces and seems to dive better.

When you draw a breath causing a vacuum, the 2nd stage goes to work and starts a flow of air. It comes down the hose from the 1st stage, into the 2nd stage and begins its journey into the ffm. After leaving the 2nd stage, it goes through two ports which sweeps the visor keeping it clear, cools the face then enters the oral nasal cavity via two one way valves. The diver inhales the air then off gasses into the oral nasal cavity. The air cannot go back into the full face mask being blocked by the two valve discs and is forced into the 2nd stage regulator regulator. The regulator is a side mount which releases the spent air away from the face. The flow is exactly the same for non-positive and positive pressure ffm. The mask is incredible to breath and a favorite for many experts.