The National Fire Protection Association (NFPA), Chapter 33, defines a spray booth as:
“A power-ventilated enclosure for a spray application operation or process that confines and limits the escape of the material
being sprayed, including vapors, mists, dusts and residues that are produced by the spraying operation and conducts or directs
these materials to an exhaust system.” Before deciding on the size and airflow configuration of a paint spray booth,
you should first consider: the size of the parts to be painted; the finish that is required; the coatings to be applied; the
type of application system, if the paint booth needs to be enclosed; and the available budget may also be a factor.
The area where the paint booth will be placed should also taken into consideration, as oftentimes the floor space
available will be limited.
Spray booth placement:
The egress code requires a minimum
3-ft. clearance on any side of the booth
requiring personnel access (NFPA 101-
Life Safety Code). As a general rule, the
interior size of the paint booth should be
large enough to allow the painter access
to all sides of the product to be sprayed (I
recommend a minimum of 3-ft. clearance
around the part). This size rule should be
considered minimum regardless of the
application system (airless, air-assisted
airless, conventional, electrostatic or
HVLP). Electrostatic and HVLP spray
are typically applied at lower pressure
and at a closer distance so the fan pattern
could possibly be adversely affected by a
booth with a high rate of airflow.
In the market for a new spray booth?
Some things to consider.
Types of spray booths
The expected production or volume of
painting that is anticipated will affect the
general layout of the finishing area more
than the size and type of booth. Correctly
laid out, small, relatively inexpensive, open
front booths can be utilized quite effectively
in high-production shops.
Generically, there are four basic types of
paint spray booths:
1. $ Crossdraft Booth: Air enters one
end and exits the opposite end of the booth.
Note: Open Industrial Booths are crossflow
2. $$ Semi-crossdraft Booth: Air
enters through the roof at one end and exits
out the opposite end of the booth. This is
sometimes referred to as semi-downdraft
or modified downflow.
3. $$$ Side-downdraft Booth: Air
enters through the roof and exits both sides
along the floor. Also sometimes referred to
4. $$$$ Downdraft Booth: Air
enters through the roof and exits through
the floor — generally this style booth utilizes
a pit in the floor; however, this type
booth can be mounted above ground on
a basement exhaust plenum. Downdraft
booths utilize gravity as the air draft
moves directly downward through the
paint area, and this design is considered
the premier booth airflow — it is also the
Deciding on an enclosed booth or an
open-type booth should be an easy decision.
If the area around the booth is moderately
dust-free and the paint is of a fast
drying nature (i.e., lacquer), then an open
front booth will suffice. If the environment
around the booth is likely to contaminate
the paint as it is applied, or if the coating
applied is slow to dry (i.e., conventional
alkyd coating), then an enclosed booth
would be the correct choice.
The type of airflow selected may be
determined simply by the budget available,
or it may be determined by the personal
preference of the painter. Even though one
airflow design may be preferred over another,
a quality paint finish can be achieved in
all four types of paint booths when used by
a competent painter. As for the type of coating
being applied, it really will not matter
since the paint booth is only evacuating the
overspray and fumes.
A paint booth is only as good as the
filters it uses. If the booth is enclosed,
there will be intake air filters that remove
the majority of airborne contaminants. If
these filters are of a low quality or do not
seal well, you may expect to see contamination
within the enclosure. Similarly,
exhaust filters that are low quality will
allow overspray to migrate through the
You must change out dirty filters in
order to maintain proper airflow. Most
booths utilize a manometer as a visual
signal to the operator when it is time to
change out the filters. The manometer
indicates the pressure differential (in
inches) from inside the work area of the
booth (in front of the filter) and inside the
exhaust chamber (behind the filter); when
this pressure reaches the limits of the fan
(usually between ¾ to 1 in.) then it is time
to replace the filters. If the filters are not
replaced, the booth will continue to function
but with an ever-decreasing airflow.
"The world is moving so fast these days that the man who says it can't be done is generally interrupted by someone doing it."
My name is Mark.
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Last edited by wookie : 01-13-2008 at 12:05:16 AM.