Intake side. The ceiling plenum holds diffusion media, typically a polyester blanket or panel set that filters incoming air and smooths it into even downward flow. Ceiling media is the finish-quality position: when it sheds or channels, you see it in the paint first. Because Saima's catalog does not document the Gamma's panel grid, we do not quote a count or dimension here. One measured panel, or a photo of the grid with a tape in frame, lets the WERCS service team lock the size.

Exhaust side. Below the floor grates sits arrestor media, most commonly fiberglass pad or roll stock cut to the pit layout, catching overspray before air reaches the fan and stack. This is the position that loads fastest and the one that regulators and fire inspectors care about most. Pit media in legacy European booths is frequently a cut-to-size roll application, which works in our favor: even without OEM part numbers, roll media can be matched to your pit dimensions exactly.

Cycle math. Exhaust media in a working downdraft loads several times faster than ceiling media. If your Gamma still has a functioning manometer or draft gauge, change the pit media on pressure rise; if not, watch for visible overspray buildup and falling airflow at the floor. Ceiling media runs longer but should never be pushed until it sheds fibers into fresh paint.

Under EPA NESHAP 6H, a shop spraying coatings with the target metal HAPs must spray inside a filtered booth, maintain the filters, and keep records; for a legacy booth like the Gamma, a documented filter schedule from a supplier stands in where original manuals are missing. OSHA 29 CFR 1910.94(c) requires the ventilation to actually perform, meaning unblocked exhaust media and maintained airflow. NFPA 33 treats accumulated overspray as a fire load, and downdraft pits are exactly where that accumulation hides from casual inspection; a pit-media change schedule is the cheapest fire-prevention line item a Gamma owner has.