Most people clean the lint screen because they can see it. The
exhaust duct behind the dryer is easier to forget, even when it runs
through a wall, ceiling, or attic before reaching the outside. A load
that takes longer than it used to is a useful clue that the route needs
attention.
Clean the lint screen before or after every load, as the appliance
instructions direct. Look at the outside termination while the dryer
runs: the flap should open and air should move out. Remove visible lint
from the opening when it’s safely accessible. Don’t cover the outlet
with a fine screen; it can catch lint. A crushed flexible connector
behind the appliance can also restrict flow, so check the space when you
move the machine for cleaning.
Follow the entire route
The
U.S. Fire Administration advises cleaning the lint filter and vent
pipe and notes that lint buildup can lead to fire. Have the full
exhaust path cleaned on a schedule suited to use, length, bends, and the
dryer’s instructions. Ask a qualified dryer-vent contractor to check the
duct material and termination if you cannot trace it, if the run is
concealed, or if drying remains slow after cleaning. Gas dryer exhaust
and connector work deserve particular care.
A ventless dryer has a different condenser, reservoir, and filter
routine; follow that model’s manual instead of applying ducted-dryer
advice. Keep your cleaning records with the appliance paperwork so a
future owner knows what was done.
I list local service contacts on Helpful
Resources. My Homeowner
Tools & Supplies page has useful maintenance basics, but no
brush kit replaces a qualified cleaning of a long, concealed route.