How often should you clean a dryer vent?

Why this one is different from the other cleaning jobs

Lint is dry and it burns easily, and a dryer works by pushing hot air through a duct that collects it. Restrict that duct and two things happen at once: the lint accumulates faster, and the heat that used to leave the house stays in it.

That combination is why dryer vents appear on fire service advice lists everywhere, and why this is the one laundry task worth putting on a schedule rather than doing when you think of it. The lint screen catches a good share of it, but never all, and what gets past goes into the duct.

What makes a duct clog faster

• Length and bends. A short straight run out through the wall behind the dryer stays clear for a long time. A run that climbs through a ceiling, crosses a floor and exits at a gable has many more places for lint to catch.
• Flexible foil or plastic duct. The ribbed inside of a flexible duct holds lint the way a rigid smooth one doesn't, and it can crush behind a dryer that has been pushed back too far. Rigid or semi rigid metal is what a vent service will want to see, and what most dryer manuals specify.
• A weak or stuck exterior flap. If the outside flap doesn't open freely, the air has nowhere to go and the lint settles. Lint packs around the hinge, and birds nest behind a flap that has stopped closing. It's the one part of the run you can see from outside, so it's worth a look on the same day you do the gutters.
• Volume. A household doing ten loads a week fills a duct roughly five times faster than one doing two.
• A run that was never really practical. Some laundry rooms sit a long way from an outside wall, and the duct wanders through a ceiling to get there. Long runs with several bends clog faster whatever you do, sometimes need a booster fan to move air at all, and are worth mentioning to a vent service so they can tell you what yours actually needs.

The signs it's overdue

What is worth doing and what isn't

Emptying the lint screen every load, and washing it occasionally if you use dryer sheets, is ordinary housekeeping and makes a real difference. Keeping the dryer far enough from the wall that the duct isn't crushed behind it is worth a look whenever you move the machine.

The duct itself is a different matter. Reaching it usually means moving the appliance, disturbing the connection, and getting a brush along a run you can't see. A vent cleaning service does that with equipment that reaches the whole length and a vacuum that catches what comes loose, and they will tell you if the duct is the wrong material or the run is longer than it should be.

What it costs to skip

The obvious cost is time and electricity: a restricted duct means longer cycles, every load, forever. The less obvious one is the dryer. Heating elements and thermal cutoffs are designed around air moving at a certain rate, and when it doesn't, they cycle far more often than they were meant to.

The reason it's on the list, though, is the failure that doesn't build up gradually. A duct packed with lint sits directly next to a heat source, and unlike most of the jobs here it can go wrong without months of warning first.

Once a year, and when to move it forward

It's the duct people forget, not the dryer. It's out of sight, and nothing about it ever looks due.

A year is the default interval in Patina. The useful thing is that you can move it: if loads have started needing a second run, bring the date forward and stop waiting for a reminder that's now telling you the wrong thing.