A Mouse in the Gas Fireplace

Why a Gas Fireplace Appeals to a Mouse

Warmth is the draw. The house mouse biology page of the Internet Center for Wildlife Damage Management says mice may nest in any sheltered location, building nests of fibrous material usually 4 to 6 inches across, and that they prefer to nest next to sources of heat such as compressors, pilot lights and hot water heaters. A gas fireplace with a standing pilot offers a warm, dark, sheltered box with a steady heat source in it.

The same source notes that mice need little or no free water, getting it from food or condensation, and that they climb well and can jump up to about 10 inches from a flat surface. A small gap is all they need to reach the compartment. And on a unit whose pilot burns day and night, the compartment stays warm every hour the pilot is on, which is exactly what the guidance says mice look for.

Where They Get In

The house mouse prevention guidance says to look for openings of 1/4 inch, because mice can enter narrower gaps than rats. Around a gas fireplace the openings are usually these:

• The hole where the gas line passes through the wall, floor or the fireplace casing, often cut larger than the pipe.
• Gaps around electrical wiring for a blower, remote receiver or switch.
• The outside vent termination on a direct-vent unit, if its guard or the wall seal around it is damaged.
• Gaps in the surround, between the fireplace and the framing or wall finish.
• A chase or attic space around the vent pipe that connects to the rest of the house.

Signs of a Mouse in the Fireplace

Mice in a gas fireplace are often found before they are seen. Watch for these:

• Droppings on the hearth, in front of the lower grille or inside the control compartment.
• Shredded paper, insulation or fabric packed under the burner or behind the grille.
• A smell of mouse urine near the fireplace.
• Scratching behind the fireplace at night.
• Controls that stopped working, which can mean chewed wiring.

One Mouse Usually Means a Route

The house mouse biology page notes that mice leave and return to their nests up to 40 times a day, exploring and memorizing their pathways to food, water and shelter. A mouse in the fireplace compartment is using a regular route from somewhere, often a wall cavity, the attic or the chase around the vent, back and forth many times a day.

That changes where you look. Check the attic around the fireplace vent pipe and any chase it runs through for droppings and torn insulation; the prevention guidance notes mice are very destructive to insulation in walls and attics. Trapping the one mouse in the fireplace without closing its route leaves the path open for the next.

Why You Should Not Simply Relight It

Nesting material packed around a burner and pilot is fuel sitting next to a flame, and it can block the air the burner needs. Rodents also gnaw. The wildlife damage guidance notes that rats living in homes gnaw electrical wiring, and a gas fireplace has wiring to its igniter, blower and controls, plus small tubing to the pilot.

So if you find droppings or nesting, turn the fireplace off at its controls, close the gas supply valve for the fireplace if you know where it is, and leave it off. If you smell gas at any point, leave the house and call the gas utility or 911 from outside. Do not reach into the compartment, vacuum around the burner, or pull out nesting material with the gas on.

Cleaning Up Droppings Safely

Rodents carry diseases, so treat droppings with care: wear disposable gloves and a mask, do not sweep dry droppings into the air, and wash your hands well afterwards. Clean the hearth and the area in front of the grille only, and bag the waste and gloves before they go in the outdoor trash. The inside of the control compartment holds the valve, the pilot assembly and the wiring, and cleaning there goes with checking them, which is technician work.

What a Technician Does

On a service visit, the technician shuts off the gas, opens the compartment and removes the nest and droppings, cleans the burner, pilot and air openings, checks the wiring and pilot tubing for chew damage, and tests the fireplace before handing it back. The vent is checked for nests at the termination. Then the entry points get closed.

The house mouse guidance is specific about materials: seal openings larger than 1/4 inch with hardware cloth, and use copper mesh or a rodent-proof fabric for small crevices. It also warns that expanding foam reduces heat loss but will not keep rodents out. Around a gas line, any material near the appliance has to suit the heat and leave the gas fittings accessible.

Prevention

Keep the gaps sealed, keep pet food and bird seed in closed containers, and check the hearth for droppings at the start of the cooler months before the first use. If you do not use the pilot in the warm months, the maker's manual for your model explains how to turn it off and relight it; a cold compartment is less inviting.

Our gas fireplace repair service covers the cleaning, the checks and the sealing. The company is local, family-owned and Proudly American, and a member of our experienced crew will look at the unit during a free inspection and write up the estimate. Until then the fireplace stays off, which is the Proudly American way to treat anything with a gas line attached.

Sources

• Internet Center for Wildlife Damage Management: house mouse biology: Nests in any sheltered location; fibrous nests 4 to 6 inches; prefer nesting next to heat sources such as compressors, pilot lights and hot water heaters; need little water
• Internet Center for Wildlife Damage Management: house mouse prevention and control: Mice enter narrower openings than rats; inspect for 1/4-inch openings; seal with hardware cloth, copper mesh or rodent-proof fabric; expanding foam will not prevent rodent entry; mice jump up to 10 inches and climb well; destructive to insulation
• Internet Center for Wildlife Damage Management: roof rat damage identification: Rodents in homes gnaw electrical wiring; disease