Technical directory · Filtration
Filter slot cleaning
Dust at the filter slot can indicate bypass around a loose filter, not merely a need for a stronger media rating.
What to observe
Remove the old filter for comparison and photograph its dimensions, arrow orientation, edge gaps and dust on the clean side.
A field example
Dust behind a recently changed filter raises a fit question. Photograph the old filter before removal and the rack after; a loose retaining door can defeat a fresh filter on the first heating cycle.
What the written work should say
The job should address fit, door closure and accessible slot debris; the replacement media must match the furnace and filter rack.
Where this task stops
A higher MERV value alone cannot close a bypass gap or fix inadequate return air.