Intake side. The ceiling plenum is the booth's clean-air plane: diffusion media across the full grid, changed as a matched set so the downdraft stays even. On finish-critical work, this is the position where media grade is most visible in the result, because everything the ceiling passes lands on wet paint.

Exhaust side. Downdraft geometry sends the overspray load through the floor, so the pit media under the grating is the fast-cycling stage and the one your manometer is really reporting on. It is also the stage your EPA capture-efficiency obligation rides on, so it gets changed on gauge reading, not on memory.

AMU stage. Blowtherm installations typically include a prefilter position in the air makeup unit, and our Blowtherm catalog notes that some older units take a headerless bag style. Identify the frame style before ordering; a header bag forced into a headerless track leaks unfiltered air around the media.

Generation check. Because the World/S record is needs-verification, we ask every first-time buyer for the same three things: nameplate photo, ceiling grid measurements, and a shot of the AMU filter track. That is enough to pin the generation and lock a verified kit to your account.

Regulatory obligations follow the booth, not its age. An older World/S is held to the same EPA 6H filter requirement as a new one: at least 98 percent demonstrated capture efficiency at the exhaust stage when spraying target HAP coatings, with filters maintained in place. OSHA 1910.94(c) requires the ventilation system to hold adequate airflow through the spray zone, which is precisely what loaded pit media erodes. NFPA 33 treats accumulated overspray in filters and plenums as fire loading. If your booth predates your ownership, a verified filter record plus dated change-outs is the fastest way to show an inspector the maintenance story.