An air respoirator charcoal filter will filter out the contaminents from an air compressor but only for a short time. What will probably end up happening is that the charcoal element will either get soaked in water or oil and render the filter medium useless. At that point you start breathing whatever the compressor spits out. Which is really not good. If you are really worried about wedling and painting fumes and want to keep the cost somewhat reasonable, look at something like a North camelback mask. The Boilermakers at work use this mask a lot over the fresh air hoods. It basically puts the filter elements on your back. That way you get the cartridges away from the welding/paint fumes and they also do not get in the way of your welding mask. If you go this way, I always use the Purple/Yellow dual cartridge North filters (filters both particulate and gases). Now if you are set on the air compressor set up, you'll probably need something like HVAC delmonic suitcase set up. We use these at work as well but the hose always seems to be a pain in the ass, especially if you are grinding. The other problem is that unit requires a lot of servicing when in use. All in all, I think for welding and painting the best would be the North Camelback respirator with appropriate filters. That way you do not have any hoses to fight with or cartridges to get in the way of your wedling mask.