2. Buffing machines are connected to particle-collecting systems providing a minimum air movement of 1,500 cubic feet per minute (cfm) (0.71 m3/s) in volume and 4,500 feet per minute (fpm) (23 m/s) in-line velocity; and
2. Adjacent storage piles shall be considered a group, and the aggregate volume of storage piles in a group shall not exceed 150,000 cubic feet (4248 m3).
Separation between groups shall be at least 75 feet (22 860 mm) wide.