Before the first fire of the year: what to check at the hearth

Burning wood leaves creosote on the inside of the flue: a brown or black deposit that starts as soft, flaky soot and, left alone, hardens into a tar-like glaze. It burns, and a chimney fire starts in it.

Five minutes at the hearth

Open the damper. It should move freely and close tight. Shine a flashlight up past it: in a straight flue you should see a patch of daylight at the top, and in any flue a clear run to the first bend.

Then look at what is on the walls. A thin, dry layer of soot is normal. Thick, crusty or shiny deposits, or flakes piling up on the smoke shelf behind the damper, mean it is time for a sweep.

Signs from last season

Smoke that rolled into the room instead of going up. A fire that was hard to keep going. A strong smell of old smoke on humid days. Twigs, leaves or nesting material falling into the firebox. Any one of these is a reason to have the chimney looked at before you light it again.

Why once a year

The fire safety standard for chimneys, NFPA 211, calls for chimneys, fireplaces and vents to be inspected at least once a year and cleaned when the inspection finds they need it. A chimney that is hardly used still collects nests, leaves and fallen mortar.

When it does need it, that is chimney cleaning: the flue brushed its full height, with the fireplace opening sealed so the soot goes into a vacuum and not into the room.

Gas fireplaces and wood stoves need their flues checked too. The deposits are different; the idea is the same.