Intake side. The ceiling plenum is the largest media surface on this booth and the one that sets finish quality. Full-ceiling diffusion media, typically tacky polyester in panel or blanket form, evens out the air and traps the dust that would land in your clear coat. Because the ceiling spans the cabin, this is also the biggest single line item in the MX400's filter budget.

Exhaust side. Both side walls carry arrestor media at floor level. Overspray load splits between the two runs, which sounds gentle but is not: painters tend to work one side of a vehicle at a time, so the near-side bank loads unevenly. Check both manometer legs, or both banks visually, before deciding only one side needs media.

Cycle math. With the exhaust split across two banks, each individual bank loads slower than a single rear wall would, while the ceiling cycles on cleanliness rather than pressure. Practical rule: replace side arrestors on pressure reading, replace ceiling media when finish defects or visible dust loading say so.

Fitment status. This model's slot record is flagged needs-verification, and we do not publish panel counts or frame sizes we have not confirmed. Photos of the ceiling grid and one side exhaust run, plus tape measurements, are enough for the WERCS service team to lock your kit.

Side downdraft changes nothing about your regulatory posture. EPA 6H applies if you spray HAP-containing coatings, and its 98 percent capture-efficiency filter requirement is met at the exhaust arrestor stage, both banks. OSHA 1910.94(c) cares that ventilation velocity is maintained, which on this layout means neither side run is allowed to blind over. NFPA 33 treats loaded arrestors as combustible loading, so change-out records and proper disposal of spent media matter during fire inspections. A standing filter subscription doubles as the maintenance log all three frameworks want to see.