Why length is the spec that matters. USI sold the Master in 7 and 8 meter cabins, and on a downdraft, cabin length translates directly into filter area: more meters means more ceiling plenum overhead and more exhaust floor underneath, both covered edge to edge in media. Two booths, same model name, meaningfully different consumable bills. The 7 meter is the smaller bill: the same finish quality with less media per change-out, every change-out, for the life of the booth.

Intake side. The documented ceiling format is Filtrair FF560GX at 74 by 132 inches, a progressive-density polyester diffusion panel. The number of panels across your plenum comes off the 7 meter layout and gets locked in at the first order. Replace the set as a set; a half-fresh ceiling diffuses unevenly.

Exhaust side. Roll stock, not pads: 22-gram fiberglass arrestor at 30 inches wide by 300 feet, cut to your floor grid. Roll media on a long cabin is the economical play, because one roll covers multiple change-outs and the cut always matches the grid instead of forcing panel-size compromises. Track how many linear feet one change consumes and the roll tells you exactly how many changes it holds.

AMU stage. The 8-pocket bag format (23.5 by 46 by 9) serves prefilter duty on the make-up air side. Pocket bags carry high dust capacity for their face size, which suits a booth moving as much air as a 7 meter downdraft must.

A longer cabin moves more air, and every regulatory hook scales with it. EPA 6H (NESHAP Subpart HHHHHH) requires filtered booth spraying maintained to design, and on a 7 meter downdraft that means a lot of square feet of media doing its job at once. OSHA 1910.94(c) sets ventilation requirements that a partially plugged 23-foot exhaust floor will quietly violate before anyone smells solvent. NFPA 33 treats loaded arrestor media as combustible accumulation; on roll-stock floors, that argues for full-length changes on schedule rather than swapping the visibly dirty section.