beamender99 as I recall on the generator I blew, the bags didn't inflate in the same way a balloon does. The bags filled and looked the same as an empty plastic shopping bag, i.e. not looking pressurized but not flat. I assume that is down to the low pressure produced, but then again I was at sea level, so removing 5 - 6 psi from ambient would probably make them look different. Does that make sense?!