Mice need shelter. They have many predators, including owls, cats, lizards, dogs, hawks, raccoons and skunks. They have the advantage of being able to squeeze through very small openings to gain access to human structures to escape pursuit and seek refuge from inclement weather. They are also extremely adept climbers, seeming to almost defy gravity. If you have a chimney, it is one of many ways mice can gain entry to your home.
What is a Damper
The damper in your chimney is a metal door located above the firebox. The function of the damper is to open to allow smoke and gas from a lit fire to escape up the chimney flue, while providing a mechanism while closed for preventing drafts and heat loss when a fire is not lit. The damper is adjustable via a lever or chain which is accessible through the front of the firebox. In addition to regulating air flow, a closed damper also prevents unwanted pests from entering your house through your chimney.
Can Mice Enter a Chimney?
An uncapped chimney is a welcome sign for a rodent looking for a place to build a nest. Squirrels, mice and rats are all adept climbers and consider chimneys to be hollow trees. Sometimes they climb down and sometimes they fall, but in either case, they end up on the smoke shelf, just a closed damper away from entering your living room.
Mice use cracks and crevices in your chimney to enter your attic. They build nests and breed, and as the young mice grow, they chew on wiring, duct work, insulation and wood and cause damage. Their droppings and urine leave odour and mess. A deceased mouse trapped in your home causes an unpleasant stench for the eight weeks that it takes for the body to fully decompose. Mice in your attic attract other rodents such as rats and raccoons, which may also attempt to gain access through your chimney. Mice carry disease: leptospirosis, salmonella, ricketsiallpox, lymphocytic choriomeningitis, Mousebite fever, ringworms, tapeworms and hantavirus are all transmittable by mice -- not just from a bite but from contact with urine and faeces as well.
Close your damper when your fireplace is not in use to prevent any pests from entering your home through the firebox of your chimney. Install a mesh-covered chimney cap to keep mice from entering your chimney to begin with. A chimney cap eliminates one point of entry for mice attempting to seek shelter in your home.