And before people think of using a regulated supply of air from their compressor as a source of clean air, its a bad idea. The compressed air contains a concentrated mixture of all the good and bad things already in the atmosphere, plus bits of oil vapour from the compressor and dirt from the tank etc.

Proper breathing-air filters are needed if you're going this way.

I have an extractor fan at ground level, and leave the room between coats while they flash off.