Intake side. The ceiling set is diffusion media whose job is even, gentle down-flow across the full working zone. On an older working booth, the ceiling deserves more respect than it gets: sagging or patched panels create fast and slow lanes in the air column, and those lanes print onto the finish. Replace as a complete set.

Exhaust side. The paired low side banks take arrestor media, fiberglass pad or roll stock as standard, changed left and right together so the split air column stays balanced over the vehicle. Overspray concentrates at these banks by design. Since the 8552 record is not yet field-verified in our system, the first order runs through a measurement confirmation: one frame opening measured, openings counted per side, ceiling layout noted. After that it repeats without ceremony.

Second stage and AMU. Installations with a heated AMU carry a pre-filter stage protecting the burner and blower, on its own cycle. If a previous owner added second-stage media ahead of the fan, include it in the program; a forgotten second stage quietly becomes the pressure bottleneck that gets blamed on fresh arrestor.

An older workhorse booth is held to the same rules as a new one. NESHAP 6H requires exhaust filtration operated and maintained per manufacturer recommendations with documented changes, and for a booth whose paper manual may be long gone, a standing filter program's delivery and change records are the practical substitute inspectors accept as a maintenance log. NFPA 33 concerns itself with accumulated overspray as fuel load: change both side banks before saturation and clear residue from the low plenums. OSHA 1910.94(c) requires design ventilation velocity while spraying, which loaded side banks are the usual reason for losing. Age is not a defense on any of the three; records and rhythm are.