502.7.3.2 Recirculation.
MC § 502.7.3.2
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. The solid particulate has been removed. 1.2. The vapor concentration is less than 25 percent of the lower flammable 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. In the event of shutdown of the vapor concentration monitor, 100 percent of the air volume specified in Section 510 is automatically exhausted.
2.Air exhausted from spraying operations is allowed to be recirculated as makeup air to manned spraying operations where 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 pose a life safety hazard to personnel inside the spray booth, spraying space or spray room.
