The answer is not to use flammable lubricants with high-pressure equipment. VERY BAD THINGS happen if you do, as you can see. Firstly, oil in an HPA system can be sprayed into an aerosol (a mist of oil) which ignites very easily due to having plenty of air to react with; secondly the heat produced by compression/flow of air can kick-start the combustion process.
There are oils and lubricants specifically intended for air systems which do not mist easily, and have much higher ignition temperatures, thus avoiding the risk. I believe (but don't hold me liable if someone kills themselves after reading this and not checking up for themselves) that oils recommended for paintball equipment are safe for use with HPA systems.
Needless to say, anyone using standard lawnmower oil in their fill rig or compressor is a danger to themselves and others.
If in doubt about your fill system or one you use, get in touch with H-PAC or the company that supplied it, and they will should have the answers.