Fireplace Safety: What You Need to Do Before You Light the First Fire of the Season

Published:May 16, 2026 · Reviewed by Koray Korkut, Fire Department Director

Every fall, the same pattern repeats: a family lights their first fire of the season in a fireplace that sat unused for eight months, and something goes wrong. A chimney fire from accumulated creosote. Carbon monoxide from a blocked flue. A spark on the carpet because the damper wasn't adjusted correctly. These are not freak accidents. They are the predictable result of skipping the inspection that should happen before the first burn of any season.

A fireplace used correctly is one of the safer things in a home. Used without maintenance, it is an open combustion device connected to an unmonitored flue system running through the interior structure of the building. The difference between those two descriptions is about 90 minutes of inspection and preparation, done once per year.

Before You Light: The Pre-Season Inspection

A certified chimney sweep inspection before the first burn of the season is the single most effective fireplace safety measure available. They check for creosote buildup, structural cracks, animal nesting, blockages, and damper condition — all things that cannot be assessed from inside the firebox.

Before you use a fireplace that has not been used since last spring, these are the things that need to be checked — either by you or by a certified chimney professional:

The chimney cap and top

Animals build nests in chimneys over summer. Birds, squirrels, and raccoons find the protected top of an unused chimney to be excellent shelter. A nest blocking the flue prevents combustion gases from exhausting and sends carbon monoxide into the home. From outside or from a safe vantage point, verify the chimney cap is in place and undamaged. A missing or bent chimney cap is an open invitation for animals and debris. If you cannot see the top of the chimney clearly, a professional inspection is warranted.

The flue — from inside

Open the damper (more on the damper shortly) and use a flashlight to look up into the flue from inside the firebox. You are looking for: visible daylight at the top (good — means the flue is open), significant dark buildup on the flue walls (that is creosote — needs evaluation), any debris visible, and the general condition of the flue liner. You cannot see the full flue from the firebox, but you can identify obvious problems. If you see heavy black buildup, animal material, or debris that you cannot explain, do not use the fireplace until a professional has inspected it.

The damper

Open and close it. It should move freely and close completely. A damper that is stuck partially open wastes heat. A damper that will not close completely allows conditioned air to escape year-round. A damper that will not open fully restricts draft and causes smoke to enter the room. If the damper is difficult to move or does not seat properly when closed, have it serviced before use.

The firebox itself

Look at the interior walls of the firebox. Cracks in the refractory panels (the heat-resistant panels lining the firebox) allow heat to contact the surrounding structure. Hairline cracks are sometimes acceptable — significant cracks that go through the panel entirely are not. The firebox floor should be free of ash accumulation from last season beyond a thin layer (a small ash bed actually improves fire starting, but deep accumulated ash should be removed).

The hearth and surround

The hearth extension — the non-combustible floor area in front of the fireplace opening — must be clear of rugs, furniture, and combustibles. Check that the area within 36 inches in front of the fireplace opening is non-combustible. This is code requirement and operational necessity — embers and sparks land in this zone routinely.

Creosote: What It Is and Why It Starts Fires

Creosote is the residue that accumulates in chimneys from wood combustion. When wood burns, it produces smoke that contains water vapor, unburned wood particles, gases, and tar compounds. As this smoke rises through the flue and cools, some of it condenses on the flue walls — and the condensed residue is creosote. It accumulates with every fire.

Creosote comes in three stages of development, and they are not equally dangerous:

A chimney fire is usually a creosote fire — the accumulated creosote on the flue walls ignites and burns inside the chimney. When this happens, flue temperatures can exceed 2,000°F. Chimneys are not designed to contain a creosote fire. The intense heat can crack the flue liner, transfer through to adjacent combustible structure, and ignite the home from the inside. Many chimney fires go undetected while they are occurring — more on that below.

What produces more creosote

Slow, smoldering fires produce far more creosote than hot, clean-burning fires. Wet or unseasoned wood burns cooler and smokier than properly seasoned wood. Fires that are damped down too much to restrict airflow smolder and produce excessive creosote. The practice of letting a fire smolder overnight to retain some heat is one of the most effective ways to build up Stage 2 and 3 creosote quickly. A hot fire with dry, seasoned wood and adequate airflow is both safer and more efficient.

The Damper: The One Thing Most People Get Wrong

The damper is the adjustable plate inside the chimney throat that controls airflow. It should be fully open before lighting any fire and for the entire duration of burning. It should be fully closed after the fire is completely out and the ash is cold.

The most dangerous damper mistake is closing it too soon — while embers are still glowing or while the fire is not fully extinguished. A closed damper over glowing embers traps carbon monoxide that would otherwise exhaust up the flue. Carbon monoxide accumulates in the room. People go to sleep thinking the fire is out. CO poisoning during sleep is one of the documented causes of fireplace-related deaths.

The test before closing the damper: no visible glow anywhere in the ash bed, the ash feels cool when you hold your hand a few inches above it (do not touch it), and it has been at least 12 hours since the last piece of wood was added. When in doubt, leave the damper open until morning.

The other damper mistake is forgetting to open it before lighting. Smoke begins entering the room almost immediately. People sometimes try to troubleshoot this while the fire is growing instead of extinguishing it immediately and opening the damper. If your room fills with smoke: close the glass doors if you have them, do not try to smother the fire with water (thermal shock to the firebox), and open the damper first — if this does not resolve the problem, close the glass doors and address the fire from outside or call for help.