Doug,
Sorry about the conflicting terms there,
I was referring to Negative Pressure as demand use, not a fully pressurised mask as in Positive pressure.
The Regulator on our BA sets is connected to the mask itself and has a knob that we turn, to change between Demand and Positive Pressure.
We also have a very strict SOP (28) here in the NZFS about the use of BA sets by Volunteer Fire Crews, using a BA set at an incident, the Cylinder is required to be recharged to thier original pre-response pressure of 190 atmospheres, before that BA set even leaves the Station again.
BTW, Doug, how quickly can you don a BA mask, if something does go wrong?.
WE are told that either you are wearing BA or you aren't, there are no half measures over here.
