Smoking Fireplace? Let's Find Out Why.
We measure draft instead of guessing at it. If smoke rolls into your room, or your home smells like a fireplace, we find the cause with instruments, not trial and error.
Why Fireplaces Smoke
A chimney works because hot gases rise and pull smoke up and out. That pull is called draft. When draft is weak or reversed, smoke comes back into the room. The most common causes we find in St. Louis and St. Charles homes:
- Negative house pressure: kitchen and bath exhaust fans, clothes dryers, and tightly sealed newer homes can pull air down the chimney
- A cold flue: especially on exterior masonry chimneys, cold air sits in the flue until it warms up
- Blockages: creosote buildup, a clogged cap screen, leaves, or an animal nest
- Damper problems: a damper that doesn't fully open, or a broken damper plate
- Chimney height or size: a chimney that is too short for the roof or too small for the fireplace opening
- Wind and nearby trees or rooflines that push air down the chimney
Smoke in the room means combustion gases, which can include carbon monoxide, aren't venting properly. Stop using the fireplace until the cause is found, and keep working carbon monoxide alarms in your home.
How We Diagnose a Smoking Fireplace
- Draft measurement: a Wöhler DM 602 digital manometer measures the chimney's draft directly, with exhaust fans and appliances on and off, so we can tell whether the chimney or the house is causing the problem
- Camera scan: our Wöhler VIS 350 inspection camera checks the full flue for blockages, offsets, and damage
- Thermal imaging: a FLIR thermal camera shows where heat and air are moving
- Laser measurements: chimney height above the roof and the size of the fireplace opening
Every finding goes in a written report, based on St. Louis City & County and St. Charles City & County currently adopted municipal code. See every instrument on our diagnostic tools page.
Which Service to Book
Hearth Diagnostic Plus includes a complete Level 2 inspection plus draft measurement, thermal imaging, and moisture mapping, which is the best way to find the cause of a smoking fireplace. If you'd like to start with a sweep and camera scan, the Core Inspection is $299. Not sure? Try our Service Finder.
Frequently Asked Questions
A cold flue is full of heavy, cold air, so smoke can roll into the room until the flue warms up. Other common causes are a house under negative pressure from exhaust fans or a tight building envelope, a damper that isn't fully open, a blocked flue or cap, or a chimney that is too short or too small for the fireplace opening.
It can be. Smoke entering the room means combustion gases, which can include carbon monoxide, are not venting the way they should. Stop using the fireplace until the cause is found, and make sure you have working carbon monoxide alarms.
Sometimes. If the cause is a heavy creosote buildup, a nest, or a blocked cap, a sweep may solve it. If the problem is draft, house pressure, or the size or height of the chimney, sweeping alone won't fix it, which is why we measure draft directly.
We measure the chimney's draft with a digital manometer under different house conditions, such as with exhaust fans on and off, scan the flue with our inspection camera, and check heat and moisture with thermal imaging. Measurements tell us whether the problem is the chimney, the house, or both.
Hearth Diagnostic Plus ($529) includes a complete Level 2 inspection plus draft measurement, thermal imaging, and moisture mapping. If you'd like to start with a sweep and camera scan, our Routine Chimney Sweep & Core Inspection is $299.
Fix Your Smoking Fireplace
Book online anytime, or call 636-946-1622, Monday through Friday 8 AM to 4 PM and Saturday 9 AM to 1 PM.