Exhaust staging, the part shops get wrong. The fiberglass roll is stage one: the cheap, thick (4-inch) progressive-loading layer that catches the bulk of the overspray. The dry poly pads behind it are stage two, a thin (1-inch) polishing layer protecting the fan and stack. Run correctly, the fiberglass changes on a short cycle and the poly on a long one. Stretch stage one past loaded and the overspray blows through and kills the poly early, and the poly is the format that comes in 20-plus-foot pieces. Replace the full stage-one run each cycle.

Intake side. Two Filtrair FF560GX ceiling runs at 60 by 312, with a 60 by 342 length in the same media also documented for longer configurations. FF560GX is a progressive-density polyester diffusion media; its job is laminar, even downward air over the vehicle. Confirm which length your plenum takes before the first order, then it never changes.

AMU stage. The 30 by 60 pocket-bag prefilters guard the make-up air unit. The five-per-case option exists because these should be turning over regularly; a shop burning one case a year is probably running them too long.

Two-stage exhaust is where NFPA 33 gets concrete for this booth: accumulated overspray in the exhaust path is a combustible deposit, and the standard expects it controlled and removed on a schedule, which is exactly what the fiberglass-then-poly train does when both stages cycle on time. EPA 6H (NESHAP Subpart HHHHHH) requires collision spraying to happen in a filtered, ventilated booth maintained per design; on the Performance, "per design" means both exhaust stages present and within loading limits, not just one. OSHA 1910.94(c) sets the ventilation requirement that failing exhaust media quietly erodes, since a plugged exhaust train drops face velocity long before anything alarms.