25 October 2004
the 25 percent of the LEL. Note that the quantity of off gassed vapors is higher early in
the drying process, tapering off at the end of the drying cycle. Refer to ANSI Z9.7 for
exhaust air re-circulation requirement.
Grinding Mode. Provide vacuum exhaust grinding tools to remove dust
during operations. The grinding process should be controlled separately from the
painting and drying processes. When feasible, grinding should be performed in a
separate grinding booth.
Ventilation System Configurations. Design or specify the entire
exhaust air system using criteria for a crossdraft hangar configuration. Figure 10-1 is
one method of designing hangar airflow distribution. When considering alternatives to
the perforated supply plenum doors, the designs should introduce the make up air in a
laminar manner and minimize the creation of dead air pockets. This will help to capture
the paint overspray and reduce the possible build up of contaminants.
Figure 10-1. Crossdraft corrosion control hangar.
Size each plenum take-off for no more than 2.44 m (8 ft) of plenum width (W).
Size the exhaust plenum for a maximum plenum velocity of 5.08 m/s (1,000 fpm).
Size the replacement air plenum for a maximum plenum velocity of 2.54 m/s
See Figure 10-2 for hangar doors and exhaust plenum details.