Technical directory · Ducts
Return grille cleaning
Return grilles gather lint because room air moves inward; that visible lint is not by itself evidence of contaminated ducts.
What to observe
Compare dust on the grille face with deposits inside the return boot and behind the filter.
A field example
Lint at a hallway return is expected where air is pulled inward. Look inside the return and at the filter's downstream side before inferring the whole air system is contaminated.
What the written work should say
An accessible grille may be cleaned as housekeeping, while deeper return-system work requires an identified reason and scope.
Where this task stops
Do not approve a whole-house duct package solely because one return grille is dusty.