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reduce paint overspray, help control workers' exposure, and protect the paint finish.
Workers must use appropriate respiratory protection irrespective of the airflow rate. On
9 February 2000, OSHA issued an interpretation of 29 CFR 1910.94 and 1910.107,
Spray Finishing Using Flammable and Combustible Materials for determining the airflow
rate required for a walk-in paint booth. In accordance with OSHA's interpretation letter,
following NFPA 33 will provide protection from fire and explosion. The guidance listed
in Subpart Z of 29 CFR 1910.94 provides protection for workers. See Appendix B for
a. Use the Painting Operations section in the ACGIH IV manual to
determine the design volumetric airflow rate. Ensure that this design
volumetric airflow rate will keep the concentration of vapors and mists in
the exhaust stream of the ventilation system below the 25 percent of the
LEL. See 1910.94(c)(6)(ii) for an example of airflow rate requirement
Do not re-circulate exhaust air while painting.
. The two main ventilation system configurations
are downdraft and crossdraft. In a downdraft booth, air enters through filters in the
ceiling of the booth and leaves through filters that cover trenches under a metal grate
floor. In a crossdraft booth, air enters through filters in the front of the booth and leaves
through filters in the back of the booth. Both configurations are commercially available.
Downdraft Paint Spray Booths. Downdraft booth configuration provides
a cleaner paint job than the crossdraft booth configuration and controls exposures to
workers better than crossdraft booth configuration. The downdraft configuration should
be the primary choice in designing or selecting of paint spray booths. Figure 9-1 is an
example of a downdraft configuration.
Crossdraft Paint Spray Booths. The crossdraft paint spray booth
usually requires less total volumetric airflow rate than the downdraft spray paint booth
because the vertical cross-sectional area of the booth is often smaller than the booth
footprint area. Figures 9-2 and 9-3 are examples of drive-through crossdraft paint spray