Animals in the Chimney: Why an Uncapped Flue Is an Open Invitation
An uncapped chimney is, from an animal’s point of view, a sheltered vertical shaft with rough walls, no predators and a warm building attached. It is close to ideal nesting habitat. Most homeowners in the southwest suburbs discover this the same way — a scratching sound above the damper, or a smell that arrives in warm weather and will not go away.
By Dan Joel, Elite Sweepers Inc.
How to tell what has moved in
The short answer: the sound and the timing usually identify the tenant. Rapid scratching and fluttering during daylight, often with chirping, points to birds. Chimney swifts in particular nest in flues and produce a distinctive chattering. Heavy scraping and thumping, especially at dusk and through the night, suggests a raccoon, which is strong enough to climb a flue and commonly brings a litter. Quick scampering during the day, with activity concentrated in early morning, is more typical of squirrels. A buzzing that grows through the summer means a wasp or bee colony rather than an animal.
Why nesting material is a genuine hazard
The short answer: it blocks the flue, and a blocked flue sends exhaust into the house. Nest material is dry twigs, leaves and grass packed into the one channel your fireplace or heating appliance depends on. That creates two problems at once. It is extremely combustible, sitting directly above a firebox. And it obstructs the path that combustion byproducts, including carbon monoxide, use to leave the building. A gas appliance or furnace sharing that chimney will keep running while its exhaust backs up, which is the dangerous version of this problem because there is nothing to see or smell.
The smell that shows up in summer
The short answer: an animal odour in warm months usually means something is in the flue, alive or otherwise. A sour, musky or decaying smell that intensifies with humidity is different from the sooty smell of creosote. Animals that fall into a flue frequently cannot climb back out, particularly if it is a slick metal liner rather than rough masonry. The result is exactly what you would expect, and the odour will not resolve until the flue is cleared.
Do not light a fire to move them out
The short answer: it is ineffective, inhumane and creates a fire risk. Smoking out an animal that cannot escape does not work, and burning a fire beneath a packed nest is how a straightforward problem becomes a chimney fire. It is also worth knowing that some species have legal protections during nesting season, and chimney swifts are among them. The correct sequence is to have the flue inspected, have the animal and the nesting material removed properly, and then close off the access.
A cap is the permanent fix
The short answer: removal solves today, a cap solves permanently. Clearing a nest without capping the flue means repeating the exercise next season, because the same features that attracted one animal attract the next. A properly sized cap with mesh sides keeps birds, raccoons, squirrels and bats out while still allowing the chimney to draft, and it keeps rain off the smoke shelf at the same time. Fitting a chimney cap is a small job that eliminates an entire recurring category of problem. If you have heard anything up there, start with a chimney inspection so the flue is confirmed clear before burn season.
Elite Sweepers Inc is insured and bonded, and you get the price up front before any work starts — nothing changes at the end of the visit. We cover Homer Glen and the surrounding southwest suburbs, including chimney sweep service in Tinley Park, and we answer the phone seven days a week from 7 AM to 7 PM. Call (708) 432-3977, or review our chimney service pricing first.
Frequently asked questions
How do I know if an animal is in my chimney or just on the roof?
Sound travelling down a flue is distinctive — it echoes and seems to come from inside the wall or above the damper rather than overhead. Opening the damper slightly usually makes it much louder if the source is in the flue, though do not open it fully if you suspect something could drop into the room.
Can I remove a bird nest from my chimney myself?
It is not advisable. The nest is usually well above reach, dropping material into the firebox does not clear the flue, and some nesting birds are legally protected at certain times of year. Professional removal also confirms nothing remains lodged higher up.
Will a chimney cap stop birds from getting in?
Yes, that is one of its primary functions. A cap with mesh sides blocks birds, squirrels, raccoons and bats while still allowing exhaust to exit. It has to be correctly sized and secured, since a loose or undersized cap can be dislodged.
Why does my chimney smell like an animal in the summer?
Either something is in the flue, or humidity is amplifying organic material left behind from a previous nest. Warm damp air moving down a cool flue carries those odours into the room, which is why the smell is far stronger in summer than in winter.
Are chimney swifts protected?
Chimney swifts are migratory birds with legal protections, and nests with eggs or young cannot simply be removed during nesting season. Timing the work correctly and capping afterwards is how the problem is handled properly rather than repeatedly.
Can animals get past a damper into my house?
Yes, particularly bats and small birds, and raccoons can force a damper that does not seal well. If something has entered the living space, close interior doors to contain the room and leave an exterior door or window open before opening the damper further.
Does a nest in the chimney affect my furnace?
It can, if the furnace vents into that chimney. This is the scenario that concerns us most, because a furnace will continue operating with an obstructed flue and there is no visible smoke to warn you. Carbon monoxide alarms are essential in any home with a fuel-burning appliance.
How often do capped chimneys still get animals?
Rarely, provided the cap is intact and properly secured. What we do see is caps that have corroded, lost their mesh or been loosened by wind, which lets the problem return. Checking the cap is part of an annual inspection.
Published August 14, 2026