Fireplace damper: what it does, how to work it, what it costs
A fireplace damper is the hinged metal plate or valve that seals the fireplace when it is not in use, in the words of the Chimney Safety Institute of America (CSIA), and it should be fully open before you light a fire. CSIA says to look up into the fireplace with a flashlight to check that it is open first. The Massachusetts Department of Fire Services says a closed damper will result in an accumulation of smoke and carbon monoxide in the home, and not to close it until the fire is out and the embers are cold. Fixr puts a new damper at $150 to $500.
| Situation | Damper | Source |
|---|---|---|
| Before you light a fire | Fully open, checked with a flashlight | CSIA |
| Fire burning, or hot ashes in the fireplace | Open | Massachusetts Department of Fire Services; Milwaukee Fire Department |
| Fire out and embers cold | Close | Massachusetts Department of Fire Services |
| Fireplace not in use | Closed, to seal the fireplace | CSIA; U.S. Fireplace Products |
| Smoke smell in the home from a wood-burning appliance | Shut down the appliance, open a window, be sure the flue is open, check the chimney, call a sweep | U.S. EPA Burn Wise |
| Chimney fire | Call 911, then close the damper after any attempt to put the fire out | Livermore Fire Protection District |
| Gas logs in a wood-burning fireplace, in the City of Fairfax, Virginia (vented gas logs), and San Jose, California | Fixed open in those two cities | City of Fairfax, Virginia; City of San Jose, California |
What does a fireplace damper do?
CSIA calls the damper a hinged metal plate or valve used to seal the fireplace when it is not in use, and says that if it is not functioning correctly, or is closed when you light a fire, you could have a smoky room at best and a fire hazard at worst. The fuel gas chapter of the 2021 International Residential Code (IRC) defines a damper more broadly, as a manually or automatically controlled device to regulate draft or the rate of flow of air or combustion gases.
Closed, it also keeps heat in. U.S. Fireplace Products, maker of the Top Damper, says closing the damper when the fireplace is not in use will prevent heated or air-conditioned air from escaping out the chimney. Fixr says a damper that is not closing can raise energy bills.
Fireplace damper vs flue
The flue is the passage; the damper is the plate across it. The 2021 IRC defines a chimney as a primarily vertical structure containing one or more flues, for the purpose of carrying gaseous products of combustion and air from an appliance to the outside atmosphere. Fixr describes a damper as a metal plate that is moved to allow or prevent the smoke from the fireplace into the flue, and says most dampers are installed a foot above the opening of the fireplace.
How to open chimney flue
- Open it before the fire, not after. CSIA says the damper should be in the fully open position before you light your fire, for safety reasons, and that if you wait until a fire is lit to check, it will be much more difficult to open the damper safely.
- Look up with a flashlight. CSIA says to always look up into the fireplace with a flashlight to check that the damper is open first.
- With a cable-operated top damper, check the lug. For its Top Damper, U.S. Fireplace Products says to pull the handle down slightly and release it, so the lug pulls up and hangs freely about 7 inches above the bracket. If the lug hangs only 1 to 2 inches above the bracket, the damper may not be open.
- Then light the fire. CSIA says to light it once you have confirmed the damper is open. The Top Damper manual warns not to start a fire if the damper is not clearly open, because that may cause smoke damage.
Open it all the way. Fixr says to open the damper to its maximum capacity before starting the fire, and CSIA lists failing to open the damper wide enough among the ways air supply gets restricted, which can speed the buildup of creosote on the flue walls.
How to close chimney flue
Close it only when the fire is fully out. The Massachusetts Department of Fire Services says not to close the damper until the fire is out and the embers are cold. The Milwaukee Fire Department says never to close your damper with hot ashes in the fireplace, because a closed damper will help the fire heat up again and will force toxic carbon monoxide into the house; it also says to be sure the fire is out before you go to sleep.
Fixr's chimney inspection guide says: "After the fire is extinguished, close the damper and wait for the area to cool before removing the ashes." Livermore Fire Protection District also lists closing the damper too early among burn habits to avoid.
On a Top Damper, U.S. Fireplace Products says to close it after the fire is completely out by pulling the handle down until the lug is below the bracket, moving the cable into any notch in the bracket and releasing the handle.
Should fireplace damper be open or closed?
Open whenever there is a fire, hot ashes or warm embers in the fireplace; closed when the fireplace is cold and not in use. CSIA describes two problems a closed top-mounted damper can help with:
- A fireplace that smells. CSIA says the odor comes from creosote deposits in the chimney and is usually worse in summer, when humidity is high and the air conditioner is on. It says the real problem is air being drawn down the chimney, and that a tight sealing top-mounted damper can also reduce airflow coming down the chimney, reducing odor.
- Smoke from an unused fireplace. CSIA says a fireplace in use in a tight house can pull make-up air, and smoke, down an unused fireplace's chimney. Its best solution is make-up air for the house, which it says also removes the potential for carbon monoxide to be drawn back down the furnace chimney; its secondary solution is a top-mount damper on the fireplace used least, kept closed.
Do gas fireplaces have dampers?
Two city building departments we read, the City of Fairfax, Virginia, and San Jose, California, require the damper of a wood-burning fireplace to be fixed open under gas logs. The City of Fairfax, Virginia, says a wood burning masonry fireplace which is to have vented gas logs installed must have the damper secured in the open position by welding it open, or by attaching a positive hold open device. San Jose's Planning, Building and Code Enforcement department says that for gas logs in a fireplace, the chimney damper must be blocked open to prevent full closure, ensuring ventilation.
We did not find a damper rule for gas logs in the 2021 IRC fuel gas chapter (Chapter 24). Its section G2432.1 says decorative appliances for installation in approved solid fuel-burning fireplaces shall be listed in accordance with ANSI Z21.60/CSA 6.26 and shall be installed in accordance with the manufacturer's instructions. Section G2427.13, a rule about vent connectors rather than fireplace dampers, says a manually operated damper shall not be placed in the vent connector for any appliance. The IRC text we read points to the log set's installation instructions, and Fairfax and San Jose add their own rule.
The Top Damper is not meant for gas: its manual says it is not for use on any type of gas burning fireplace or appliance, and to check local codes and the appliance manufacturer before installing on flues venting gas fireplaces.
Do all fireplaces have dampers?
Masonry fireplaces built to the 2021 IRC do. Section R1001.7.1 says: "Masonry fireplaces shall be equipped with a ferrous metal damper located not less than 8 inches (203 mm) above the top of the fireplace opening. Dampers shall be installed in the fireplace or the chimney venting the fireplace, and shall be operable from the room containing the fireplace." Factory-built fireplaces follow their listing: R1004.1 says they shall be listed and labeled and installed in accordance with the conditions of the listing. The code binds only where it is adopted.
Some cities add their own rule. In Los Angeles, for a chimney repaired inside a municipal airport noise boundary, the prescriptive standard the Department of Building and Safety lists for the 65 to 70 dB noise band says each masonry fireplace shall be fitted with a damper at the top of the chimney that is operated from the firebox, plus glass doors across the front of the firebox.
Types of fireplace dampers: throat and top-sealing
| Damper in the fireplace throat | Top-sealing damper (Top Damper example) | |
|---|---|---|
| Where it sits | In the throat, which the 2021 IRC places not less than 8 inches above the lintel (R1001.7) | Glued to the top of the flue liner with the supplied adhesive, which sets for 24 hours |
| How it is worked | From the room containing the fireplace, which the 2021 IRC requires of masonry fireplace dampers (R1001.7.1) | A cable down the flue to a bracket drilled into the firebrick about 20 inches off the firebox floor |
| Cleaning | Fixr says it is unhinged or unpinned to clean, though some are not removable and are cleaned in place | Maker recommends a CSIA certified sweep install it and clean the chimney at the same time |
| Gas fireplaces | Fairfax and San Jose require the damper fixed open under gas logs | Not for use on any gas burning fireplace or appliance, per the maker |
U.S. Fireplace Products says its Top Damper is made of aluminum and designed to help save on heating and cooling bills, help prevent down-drafts and odors, keep out rain, snow, birds and pests, and help reduce outside noise. HomeGuide lists a damper among chimney cap features, at $140 to $420 installed, and says it stops cold air from blowing into older fireplaces. Cap prices and types are in chimney cap cost.
Fireplace damper replacement cost
| Job | Price | Source |
|---|---|---|
| New damper | $150 to $500 | Fixr, chimney cleaning cost guide, updated January 31, 2025 |
| Damper as a chimney cap feature, installed | $140 to $420 | HomeGuide, chimney cap cost, February 9, 2026 |
| Fixing smoke coming into the house (Fixr says the cause could be a damper problem, a flue blockage or a cap issue) | $150 to $1,000 | Fixr, fireplace repair cost, updated January 31, 2025 |
Fixr does not say whether its $150 to $500 for a new damper includes installation. Neither price guide we read gives a separate price for repairing a damper rather than replacing it. HomeGuide names rust on the damper or firebox among the warning signs a chimney needs repair, and downdrafts as a sign of a failing chimney damper. Fixr lists rusty or damaged dampers among its examples of what a chimney inspection report can include, and names a faulty or closed damper as one possible reason you cannot start a fire. CSIA lists warped metal of the damper among the signs of a past chimney fire, and says to call a CSIA certified chimney sweep if you think one has occurred; what to do during one is in chimney fire.
A damper check is part of a chimney inspection, a chimney sweep can clean one, and other repair prices are in chimney repair cost. To have a damper that sticks, rusts or will not seal looked at, use the form below and we will send your request to a company that serves your ZIP code.
Fireplace damper: common questions
Can you leave fireplace damper open overnight?
How to tell if fireplace flue is open
When to close fireplace damper after fire
Can you use a fireplace without a damper?
How much does it cost to repair a chimney damper?
Sources
- Chimney Safety Institute of America, Homeowner resources and FAQs ("How do I work my damper?", fireplace odor, smoke from a second fireplace, gas chimneys): csia.org
- Chimney Safety Institute of America, "Preventing Chimney Fires": csia.org
- International Code Council, 2021 International Residential Code, Chapter 10, Chimneys and Fireplaces (R1001.7, R1001.7.1, R1004.1): codes.iccsafe.org
- International Code Council, 2021 International Residential Code, Chapter 24, Fuel Gas (definitions, G2427.13, G2432.1): codes.iccsafe.org
- Massachusetts Department of Fire Services, "Fireplace, wood stove, and chimney safety": mass.gov
- Milwaukee Fire Department, safety message: milwaukeefd.com
- Livermore Fire Protection District, "Chimney Fires": livermorefireco.gov
- U.S. EPA Burn Wise, Wood-burning installation and maintenance: epa.gov
- City of Fairfax, Virginia, gas pipe installation notes for fireplaces: fairfaxva.gov
- City of San Jose, Planning, Building and Code Enforcement, Mechanical projects: sanjoseca.gov
- Los Angeles Department of Building and Safety, Chimney repair: permitla.org
- U.S. Fireplace Products, The Top Damper installation and operation instructions, 2020 (PDF hosted by Zoro): zoro.com
- Fixr, Cost to Sweep a Chimney, updated January 31, 2025: fixr.com
- Fixr, Chimney Inspection Cost, updated August 29, 2025: fixr.com
- Fixr, Fireplace Repair Cost, updated January 31, 2025: fixr.com
- HomeGuide, chimney cap cost, February 9, 2026: homeguide.com
- HomeGuide, chimney sweep cost, February 9, 2026: homeguide.com
- HomeGuide, chimney repair cost, January 22, 2026: homeguide.com