Why Won't My Fire Stay Lit in the Fireplace?

What a fire needs to keep going

A wood fire is a small engine. The heat breaks the wood down into gases, the gases burn above the logs, and that flame heats the next layer of wood. To keep the cycle running, the fire needs fuel that gives up its gases readily, a steady supply of oxygen from the room and a chimney that carries smoke away fast enough for fresh air to replace it.

Draft is the chimney's part. Hot gases in the flue are lighter than the cooler air outside, so they rise, and as they rise they pull room air into the firebox. A warm, tall, clear flue draws strongly. A cold, short or obstructed one draws weakly, and a weak draft lets smoke linger around the logs, robbing the flames of oxygen.

Start with the wood

Damp wood is the most common cause by a wide margin. Water in a log has to boil off before the wood can burn, and that takes heat away from the fire. Wet wood sizzles, hisses, bubbles at the ends, makes white or gray smoke and blackens without catching. Wood that was cut recently, left uncovered in the rain or stacked on bare ground can be wet inside even when the bark looks dry.

Split a log and feel the fresh face. If it is cool and damp, it will struggle. Well-seasoned wood is lighter for its size, often shows cracks across the ends, and two pieces rapped together give a sharp crack rather than a dull thud. An inexpensive moisture meter pressed into a freshly split face takes the guessing out of it.

How the fire is built

A couple of large logs with a handful of newspaper underneath rarely get hot enough to sustain themselves. A fire needs a bed of small, dry kindling that builds heat quickly, then split pieces of increasing size. Logs laid tight together or flat on the grate leave no path for air between them, and a fire with no air channels starves even with good wood.

Many people get better results from a top-down fire: larger splits on the bottom, smaller pieces above and kindling with paper on top. It burns downward, heats the flue early and needs less tending. A thin layer of ash under the grate helps insulate the coals, but an ash bed piled up to the grate chokes the air coming from below.

Leave a little space between pieces as you add wood, and add it before the coals have burned down to a dull glow. A fresh log dropped onto a weak bed of coals cools the fire faster than the coals can heat it.

Not enough air in the room

Fire takes its air from the room, and the room takes it from the rest of the house. Closed glass doors, or doors whose air vents are shut, cut the supply sharply. In tighter houses, the kitchen range hood, bathroom fans, a clothes dryer or a boiler firing in the basement all pull air out of the same house the fireplace is drawing from, and the fireplace can lose that contest.

A simple test settles it. Open the glass doors, open the damper fully, and crack a window a little in the same room. If the fire suddenly perks up, air supply was the problem. Turn off exhaust fans during a fire and see whether that alone makes a difference.

The damper and a cold flue

Check the damper next. One that is only partly open, or whose plate has slipped or rusted on its pivot, holds smoke in the firebox. Look up with a flashlight and confirm the plate is fully open, not just the handle. On a top-sealing damper, check that the cable is fully released and the lid at the top has opened.

Then think about temperature. An exterior chimney on a freezing night holds a column of cold, heavy air that has to be pushed out before the flue starts to draw. Holding a lit roll of newspaper up near the open damper for a minute warms the flue and often gets the draft moving before the fire is lit.

Tall houses and the stack effect

Brownstones, rowhouses and other tall homes behave like chimneys themselves. In winter, warm air rises through the stairwell and leaks out of the upper floors, which pulls air in at the lower floors and the basement. A parlor-floor fireplace can find itself competing with the whole house, and an open window or attic hatch upstairs makes that pull stronger.

Closing upper-floor windows and doors while the fire is going, and giving the fireplace room a little fresh air of its own, often helps. Where the problem is constant, a technician can look at whether the chimney is tall enough for the house and whether the flue is sized to the fireplace opening.

When the chimney is the cause

A flue partly blocked by a nest, fallen debris, broken tile, heavy creosote or a clogged cap screen gives smoke nowhere to go, and a fire smothered by its own smoke dies down. In older chimneys, a flue that is too large for a firebox that was later made smaller, or a smoke chamber with rough, stepped walls, can also make the draft sluggish.

A blocked flue is a safety concern as well as a nuisance, because smoke and carbon monoxide can be pushed back into the house. Test the carbon monoxide alarms before the next fire. An alarm, or anyone in the house feeling sick while the fireplace is going, means leaving and calling 911.

• Smoke hanging in the firebox even with dry wood and open doors
• Twigs, leaves or broken tile falling onto the grate
• A strong smell of creosote from the fireplace
• The fire burning normally for a while, then fading as smoke builds

What an inspection looks for

If dry wood, open air and a warmed flue still do not keep a fire going, stop using the fireplace and have the chimney inspected and swept. We check the damper and its seal, the smoke chamber, the full flue for blockages and buildup, the cap screen, and the height and size of the flue relative to the firebox opening. Where it helps, the draft is tested with the fireplace in use.

If the cause turns out to be the wood or the air supply, we tell you plainly, since those are fixes you can make yourself. If it is the chimney, the repair options and their cost come in writing before any work.