Spray booths

This is in response to Mr. Dixon's request for information
concerning large spray booths.  I installed a booth in my studio
several years ago.  The booth is ten feet wide, eight feet tall and
eight feet deep.  It is housed in a room  fifteen by fifteen feet. I
use the booth to treat furniture and other wooden objects.  I spray
shellac and lacquer, and use other volatile solvents like methylene
chloride, mineral spirits and so on.  Since your use is different,
I'm not sure this will help, but I thought I'd pass along my
experience.

First off, here in the states, you have to check with the city you
live in to see what the standard is for the booth you are installing
and the materials you are spraying.  There are both federal and
local codes that describe how many cubic feet per minute (CFM) you
must move through the system.  The fire department is particularly
interested in the installation, and you should touch base with them
to see what they require as well.  In addition to CFM requirements,
the fire department required I install a fire protection system
within the booth and in the exhaust stack. Don't assume the city and
the fire department necessarily have the same standards.  In some
towns, rules will be bent or overlooked, in others you must conform
to code.  It is also possible to receive a variance from the codes.
The codes are designed for booths used for eight hours a day.  In my
city, it doesn't matter to the inspectors that I only spray once
every two months or so, and for brief periods even then.  The point
is to remove flammable mists as rapidly as possible.  Slow
evacuation of out gassing vapors is not their concern.  I've often
wished I could afford to put in a separate system that would handle
outgassing.  Instead, I periodically turn on the big fan and clear
the air inside the booth.  It only takes a minute. It is also to
your advantage to remove the mist as quickly as possible because it
is much easier to spray when you have a clear field of vision.

The fan in my booth has 24 inch diameter blades.  It is Binks model
30-2408-3 hp.  1629 rpm.  It moves roughly 8100 CFM.  Mounted on the
wall of the booth which is behind me when I spray is a bank of
filters six feet by six feet.  I used furnace filters. The filters
allow an air flow into the booth from the general shop area.  I have
found that this keeps particles out of the air passing over the
surfaces I am treating.  I also wash and vacuum the walls and floors
inside the booth room very regularly. Many booths have raised floors
with drainage installed so that the booth can be hosed down
regularly.  This creates an additional toxic waste disposal problem,
but sure keeps it clean.  It sounds to me like allowing the makeup
air to come in from above may be a very good idea, though you may
still require baffles to direct the air away from your surfaces.

You must have a source of make up air.  In my booth, the inspectors
have allowed me to use an outside air intake (the filter system I
described and an open door to the outside) instead of installing an
industrial make up air system.  I imagine by now you know that a
typical make up air system can start at about $17,000.00 US.  The
regulators are concerned that you do not draw warm air from the rest
of your building, and are also concerned that you do not draw in
carbon monoxide from your heating system.  Your draw fan can also
put the pilot light out in some furnaces.  In my case, I noticed
that in the dead of a Wisconsin winter (single digit temperatures
below zero, F, during the day), I lost two degrees over a twenty
minute run of the fan.  I checked with my neighbors who noticed no
drop in temperature in their spaces at all. I didn't open the
outside door that day.

You should consider the spray gun you will use, since that will be a
factor in the amount of overspray you have to worry about.  I use a
twenty-five year old Binks model 81-350 spray gun.  It has an
efficiency of about 50 to 70 percent, meaning much of the material I
spray goes out as overspray.  I am not familiar with your particular
needs, but I would look into  HVLP (high volume, low pressure) spray
apparatus.  I believe they are about 90 percent efficient and
produce much less overspray.

I imagine your problem will be holding the work stable without
damaging the stretched canvass.  In my studio, if the bank of air
filters is closed and the fan is on, it is extremely difficult to
open the door to the booth. With the air filter bank open, you can
see the dropped ceiling tiles and other doors in the shop suck
inward.  It may well be that sufficient make up air from above your
work area will reduce or eliminate that problem.  Or maybe you won't
have to meet specific codes so that you can use a less powerful
exhaust fan.

I found the booth manufacturers most helpful in selecting a system.
Try Binks and Devilbiss.  Both are well known and reliable.  There
are other manufacturers, I'm sure.

    Binks-Bullows in Australia:  61-299-75066
    Devilbiss in USA:  708-833-5850

I have addresses for both if you need them.  Good luck.

Ian Gale
Gale-Sinex Restorations, Ltd.
Madison, WI

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                  Conservation DistList Instance 12:56
                 Distributed: Tuesday, January 5, 1999
                       Message Id: cdl-12-56-005
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