On Fri, 20 Nov 2009 08:45:32 -0800, Bruce L. Bergman
wrote:

On Fri, 20 Nov 2009 10:00:09 -0600, "hls" wrote:


"PaPa Peng" 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 --


Good advice, Bruce. Painting, especially with today's paints can be
VERY dangerous. It can also be illegal so my advice would be to check
with the local authorities as to what you are allowed to do. In
Californicate that would be very little without professional equipment
and all kinds of permits.

I've been off the group for a while. Got tired of all the political
crap. Doesn't look like much has changed. How are things with you?

Jim Chandler

On Fri, 20 Nov 2009 09:15:51 -0800, Jim Chandler wrote:

On Fri, 20 Nov 2009 08:45:32 -0800, Bruce L. Bergman
wrote:

On Fri, 20 Nov 2009 10:00:09 -0600, "hls" wrote:


"PaPa Peng" 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 --


Good advice, Bruce. Painting, especially with today's paints can be
VERY dangerous. It can also be illegal so my advice would be to check
with the local authorities as to what you are allowed to do. In
Californicate that would be very little without professional equipment
and all kinds of permits.

I've been off the group for a while. Got tired of all the political
crap. Doesn't look like much has changed. How are things with you?

Jim Chandler


Ferchrissakes, a good disposable overall, gloves and the correct filter
cartridges will cope with Isocyanate catalysed paints. I've only sprayed a
couple of gallons of the stuff over the last few weekends and I haven't died
yet.

PS positive pressure masks are banned in some parts of the world, because you
can't guarantee there will be no recirculation. Go figure.


Mark Rand
RTFM

On Sat, 21 Nov 2009 01:22:51 +0000, Mark Rand
wrote:
On Fri, 20 Nov 2009 09:15:51 -0800, Jim Chandler wrote:

Good advice, Bruce. Painting, especially with today's paints can be
VERY dangerous. It can also be illegal so my advice would be to check
with the local authorities as to what you are allowed to do. In
Californicate that would be very little without professional equipment
and all kinds of permits.

I've been off the group for a while. Got tired of all the political
crap. Doesn't look like much has changed. How are things with you?

Jim Chandler

Selective corner-cutting is encouraged in r.c.metalworking - but you
have to understand the problem before you go 'Off the reservation' for
a lower cost solution. You look at what is required for a commercial
operation, then you find a way to do the same thing without spending a
bundle doing it.

Like the lights - If you put a cheap sheet of polycarbonate plastic or
laminated glass, you don't need an explosion-proof light fixture.

The booth doesn't have to be all metal - it just has to be non
combustible enough to not catch fire easily, and fairly sturdy so a
flash fire from the solvents doesn't collapse it on top of you. Other
than that, feel free to improvise.

It could be a permnanently built room on a house or garage, with
drywall walls - but you have to provide a blowout panel or two in case
you get that flash fire. Removing the door striker and using a simple
ball catch lets it pop open.

And you always work with the EXIT door to your back so you have a
clear egress path - you don't want to go through the fire to get out,
that's bad form.

Ferchrissakes, a good disposable overall, gloves and the correct filter
cartridges will cope with Isocyanate catalysed paints. I've only sprayed a
couple of gallons of the stuff over the last few weekends and I haven't died
yet.

Yes, and I know a finish carpenter who used to make big bucks painting
airplanes. And those exotic paints screwed him up something bad, even
with a respirator - he has hand tremors that were funny when Don Knots
filmed "The Shakiest Gun In The West" but aren't fun at all when you
have to live with them the rest of your life.

He had to walk away from the paint booth and develop a totally
different craft. Luckily the tremors don't keep him from doing a
great job at finish carpentry.

PS positive pressure masks are banned in some parts of the world, because you
can't guarantee there will be no recirculation. Go figure.

They can make the perfect safety system. But if it's implemented and
used by a moron who puts the pump (and it's fresh air intake) inside a
cloud of the compromised atmosphere...

Think first about what you are doing and WHY you are doing it, and
you won't make stupid mistakes like that. If nothing else, you read
down the checklist in the instructions for the PPV Pump every time you
set it up. And when they get to the line about "Make sure to position
the unit well away from the exhaust outlet of the spray booth"...

And it's a lot easier to ban something than try to legislate that
all workers have to use their brain and follow the instructions.

-- Bruce --