Sorry to be a thread necromancer here, but I've been thinking about this for a while and think i may have a solution to the heat problem. You can pick up small computer fans for only a couple of dollars a unit and easily hook them up using a 12v battery. Depending on the style of gas mask you are using or more practically what you are sticking onto your existing paintball mask, you could easily stick one of these inside the air canister. Here is a pic of what one of the fans look like.



It would probably work best for this style of mask and you could set the fan up to blow air directly onto your face and not have to worry about air blowing up into your eyes because the goggles and seperate to the mask. Of course if you had a canister on either side of your mask you could have two.



People have used fans like these as replacements for retail mask fans and are known to be quite quiet and cheap to maintain. Anyway, thats just my thoughts. Again, sorry to raise the thread form the dead again.