This subject comes up quite a bit on the forum and people are always afraid of a fan igniting the paint fumes so I asked my friend Scooter about it since I want to make an exhaust system to take fumes out of my side door in the garage for airbrushing helmets, motorcycle tanks, etc down the road.
Here is what he told me in regards to worrying about a boxfan in the doorway to exhaust the paint from the room:
Now I in no way condone anything unsafe and I am a very safe worker on my job and at home so don’t think this is irresponsible.
I suppose some will disagree with him and Gip may have something to say about it also being that this is his area of expertise, but I trust my friend as he has been airbrushing and spray painting cars since 1962 and he is a wealth of information.
Just thought I would pass this along to maybe ease your minds if you are worried about building a spray booth for modeling. [:D]
First, I trust empirical evidence to show what works and doesn’t work. So I’m all for testing your setup (paints, volumes, flow, etc…) in a safe situation and seeing if it is safe or not.
Lot’s of factors are involved before one can tell if a given situation will or won’t ignite. Given the right compound, in sufficient concentration, I have little doubt that even the most minute spark formed by the typical open motor could produce ignition. Flash points of many organic solvents are astonishingly low - e.g. below zero F. Whether or not these conditions exist in any given paint setup can really only be determined through experimentation. I’m sure one could manage the above factors and get a setup that works without significant risk.
The main thing that I’d be concerned about is that remaining portion that does evaporate - along with whatever evaporates from the surface. Digging back to my college chemistry days, I would think it’s those gas-phase vapors, depending on the compounds involved, which are the most susceptible to ignition, not the liquid-phase mist droplets.
I talked to another guy tonight who uses a boxfan to exhaust the overspray of clears he sprays on airbrushed license plates. He said in the past 6 weeks he has cleared over 700 plates and never had a single problem.
The Mythbusters did an episode on this not long ago…well-- actually they tested the insect foggers and the chances of a house blowing up…it did take a lot to get the poof but it did happen [;)] and it was over fast.
Oooh, I do love my Mythbusters. That’s one of the few real science based, skeptical, programs on tv today. I’ve seen them do the same thing with gasoline vapors and struggle to get them to go off with a lit match in an enclosed space. Just because it’s unlikely to detonate however, doesn’t mean it’s impossible. If possible I’d want to err on the side of caution. I think what Mike is saying however, is that if money is really an object, you’ll probably be safe enough to make do with what you’ve got.
Thanks Josh.
I think also that when most things explode it is because they are in a stagnant state where they can accumulate. I think if you have that fan going from the minute you started spraying until after you were done then the possiblity of an explosion is almost impossible. The parts per million of the vapor combined with the steady flow of air makes it hard to believe that it could explode although nothing is impossible.
I would have to agree with mike. I don’t think you could get the air/fuel mixture just right for the explosion to happen. The other thing to keep in mind with these small fans is that most all of them now-a-days are induction motors. This means there are no brushes riding on armatures creating posible sparks.