What Does a Chimney Sweep Do?

What a chimney sweep is

A chimney sweep is a tradesperson who cleans and checks chimneys, fireplaces and the flues that serve stoves, inserts, boilers and water heaters. The job is about fire safety and airflow: removing the deposits that can catch fire or narrow the flue, clearing blockages, and spotting damage before it causes a leak, a smoky room or exhaust getting into the house.

A good sweep also explains what they saw in plain language, so you know whether the chimney is fine for the season or something needs attention, and whether it is urgent. The cleaning and the look at condition go together; one without the other leaves half the job undone.

Step by step on the day

The visit follows a set order. Exactly how it goes depends on the chimney and the appliance, but most fireplace sweeps look like this from start to finish.

• Drop cloths go down over the hearth and the floor from the door to the fireplace
• The fireplace opening is sealed and a vacuum runs to pull dust away from the room
• Brushes on flexible rods scrub the flue from the bottom, the top, or both
• The smoke shelf, smoke chamber and damper are scraped and cleaned
• Soot, debris, nests and ash are bagged and carried out
• The cap, crown, damper and flue are checked and the findings explained

Cleaning the parts you cannot see

Most of the buildup is not in the firebox. It collects in the smoke chamber just above the damper and on the flue walls, where smoke cools on its way up. The smoke shelf, a ledge behind the damper, catches falling soot and debris, and sometimes rainwater and animal nests. In older fireplaces the smoke chamber walls are often rough, stepped brick that holds deposits; those are scraped by hand.

Light, dry soot brushes off easily. Crunchy, flaky creosote takes stiffer brushes or rotary tools. Hard, glazed creosote may need special cutting heads or a chemical treatment over more than one visit. If the cap has a screen coated in creosote, it is cleaned too, since a clogged screen chokes the draft.

Tools and how they are chosen

Sweeps carry brushes in many shapes and sizes, because a brush has to match the flue it cleans. Square and rectangular clay flues get square brushes; round stainless liners get round brushes made so they do not scratch the metal. The rods may be fiberglass or flexible poly, joined in sections and pushed from below or lowered from the roof. Rotary systems spin a brush or flail with a drill for stubborn deposits.

The vacuum matters as much as the brush. A dedicated soot vacuum with fine filtration runs at the opening the whole time, keeping the room under slight suction so dust moves toward the fireplace rather than into the house.

• Open wood fireplace: soot and creosote, cleaned from the smoke chamber, smoke shelf, flue and cap screen
• Wood stove or insert: often heavier creosote in the connector, liner and top cap; an insert may have to be pulled
• Oil boiler or furnace: soot and acidic scale, with the smoke pipe, base and cleanout as the focus
• Gas boiler or water heater: little soot, so the cap, base and connector are checked for debris, nests and condensation
• Pellet stove: fly ash at the tees, the elbows and the base of the vent

Heating appliance flues

Many chimneys in older homes serve an oil or gas boiler or a water heater as well as a fireplace, often in a separate flue. Those flues are cleaned differently. On an oil system, the smoke pipe is taken down and cleaned, and the base of the chimney is emptied through the cleanout door, since most of the soot and scale falls there. On a gas system there is usually little to brush, but the base is checked for fallen tile, nests and water, and the cap for blockage.

The appliance is shut down while its flue is worked on, and reconnected and sealed before it runs again.

What the sweep checks

While cleaning, a sweep gets a close look at the chimney from inside and out. They look for cracked or missing flue tiles, gaps in mortar joints, a rusted or broken damper, a cracked crown, a damaged or missing cap, signs of water getting in, and signs of a past chimney fire such as puffed, honeycombed creosote or warped metal.

For a boiler or water heater flue, they also check the connector pipe, the thimble and the cleanout for blockages and condensation damage. NFPA 211 calls for chimneys to be inspected yearly, and the sweep is the natural time to do it. Anything that needs repair is explained, and you get it in writing before deciding.

Signs a sweep is due

NFPA 211 calls for cleaning when deposits build up, and the yearly inspection is how that is judged. Between visits, a few signs suggest the flue needs attention sooner: black flakes falling into the firebox, a fireplace that has started to smoke into the room, a strong smoky smell on humid days, a fire that is hard to get going or will not stay lit, and the sound of birds or animals in the flue.

On a wood stove, glass that blackens quickly and a stove that will not reach its usual temperature are common clues. On an oil boiler, soot around the burner or the barometric damper and a burner that locks out more often point to a flue that needs cleaning. Any of these is a reason to book a visit rather than wait for the usual date.

How long it takes

A single fireplace flue in reasonable shape usually takes an hour or two, including setup and cleanup. Heavy or glazed creosote, more than one flue, a wood stove or insert that has to be pulled out, or a chimney that is hard to reach from the roof all add time. A tall chimney on a steep roof may need extra safety setup before anyone climbs.

How to prepare

Do not burn a fire the day before, so the ashes are cold. Clear the mantel and move furniture and rugs back from the hearth. Keep pets in another room. If a boiler shares the chimney, know where its service switch is. If you have noticed anything, like smells, drips, noises or smoke in the room, mention it at the start so the sweep knows where to look first.