Intake ceiling. The full-ceiling plenum takes diffusion media across the working zone, usually a polyester panel set or blanket. In a true downdraft, ceiling media quality maps directly to finish quality: every particle that gets through is riding laminar air straight down onto fresh paint. This is the position where stepping up a media grade earns its price back.

Exhaust pit. Below the grating, arrestor media catches overspray before the air reaches the fan. Fiberglass pad and roll media are the standard fill; the pit format means you replace media in sections sized to the pit rather than to framed wall grids. Because slot dimensions for this model are not yet field-verified in our records, we confirm pit length, width, and media format from your measurements before shipping.

Second stage where fitted. Some pit downdrafts run a second-stage filter after the arrestor to protect the fan and stack. If your booth has one, note it in the fitment check; running a fresh arrestor in front of a saturated second stage wastes the arrestor change.

The pit changes nothing about the regulatory picture and everything about how easy it is to comply. NESHAP 6H requires spray booth exhaust to pass through filter technology maintained per manufacturer guidance, and a pit booth leaves no scheduling excuse for skipped changes. OSHA 1910.94(c) requires maintained ventilation velocity through the booth; in a downdraft that velocity is set at the floor, so the pit media condition is the compliance condition. NFPA 33 treats overspray-loaded filter media as combustible loading, and a pit full of saturated arrestor sitting below floor level is exactly the accumulation the standard wants removed on schedule. Dated change records close the loop for all three.