From: Bruce L. Bergman on
On Fri, 20 Nov 2009 10:00:09 -0600, "hls" <hls(a)nospam.nix> wrote:

>"PaPa Peng" <papapeng3(a)> wrote in message
>> The air is exhausted through two
>> furnace filters.
>Is the air filtered before entering the chamber as well?

Well, it should be filtered both ways. 'In' to the chamber for the
ultimate finish without any dust in it, and the 'out' filters are
paint pads to keep the paint out of the fan blades, but - Go look at
the paint booth at an auto body shop, study the details, and you start
to understand the scope of the problem...

I would just rig a simple "open" booth to catch the overspray, and
don't worry too much about dust. Because a closed booth gets complex
and expensive real fast. If you are going to have a person step
inside an isolated room and spray around volatiile materials (ranging
from flammable to explosive when atomized during application) you HAVE
to follow the same safety design constraints.

It has to be non-combustible construction in case of a flash fire,
and not easily collapsed on top of the painter and work by the
pressure wave, so a lot of temporary methods like draped visqueen
plastic over furring strips is OUT. You need a way out, you need
explsion-proof lighting (or the fixture outside the room shining in
through a sealed window), you need to design against static buildup
that could ignite the fumes...

You could build a little paint booth at home, but the project would
eclipse the model you are painting. It would work with a freestanding
sturdy frame of 2X4 studs with light sheet-metal screwed on the
inside, and a Lexan window on top for the outside light fiixture.
Prehung house door or two for egress hung opening out, and ball-spring
latches only so they can pop open to release the blast overpressure.

You need pro-grade fire extinguishers ready at hand, strategically
placed, and enough of them to handle the volume of materials. And a
garden hose in case that still isn't enough.

Your exhaust fan motors have to be outside the airstream, and make
sure the static can drain from the blower wheel/blade. And ground the
sheet-metal walls, and the hook or table the work sits on, and make
sure static can drain away from the paint gun...

If you spray two-part catalyzed paint, you have to use real non-
combustible paint pads on the exhaust system. (Not just furnace
filters.) These paints get hot as they cure, and you don't want your
paint booth to spontaneously combust on you.

And no spraying any exotic aircraft paints with nasty solvents
that'll kill you (like DuPont Imron) inside any booth without a full
postive pressure respirator rig. Bought, not cobbled together - there
are places to scrimp, this isn't one of them.

--<< Bruce >>--