Air exhausted from spraying operations shall not be recirculated.
Exceptions:
1. Air exhausted from spraying operations shall be permitted to be recirculated as makeup air for unmanned spray operations provided that:
1.1 Solid particulate has been removed.
1.2 The vapor concentration is less than 25 percent of the lower flammability limit (LFL).
1.3 Approved equipment is used to monitor the vapor concentration.
1.4 An alarm is sounded and spray operations are automatically shut down if the vapor concentration exceeds 25 percent of the LFL.
1.5 The spray booths, spray spaces or spray rooms involved in any recirculation process shall be provided with mechanical ventilation that shall automatically exhaust 100 percent of the required air volume in the event of shutdown by approved equipment used to monitor vapor concentrations.
2. Air exhausted from spraying operations shall be permitted to be recirculated as makeup air to manned spraying operations if all of the conditions provided in Exception 1 are included in the installation and documents have been prepared to show that the installation does not present life safety hazards to personnel inside the spray booth, spray, space or spray room.