Apollo LP respirators are for use with an ambient air pump. All Contractor machines have a working pressure rating of 150 psi, 1-1/4” piping, pneumatic pressure-release remotes and manual abrasive metering valves. Blast machine capacities, stated in pounds, refer to abrasives (such as mineral slag) which weigh about 100 lbs per cuft. Comparatively, steel grit weighs 250 lbs per cuft.