By Johnathan Mason, Ace Chimney Service.
An uncapped flue is a hollow, sheltered, vertical shaft with rough walls — which is to say, from a bird or a raccoon’s point of view, an excellent place to raise young. Every year we open Woodstock chimneys in the fall and find a season’s worth of nesting material packed into the smoke chamber. Late summer is exactly the right moment to deal with it, and here is why the timing matters.
How you know before you look
- Scratching, fluttering, or chirping in the wall behind the fireplace, loudest at dawn and dusk.
- Debris in the firebox: twigs, leaves, feathers, insulation, dropped mortar.
- A rotten or ammonia-like smell rather than the usual smoky one.
- Smoke pushing into the room from a fireplace that drafted fine last winter — a blockage in plain terms.
- Flies gathering at the fireplace opening out of season.
Who is usually up there
Chimney swifts nest in flues and are protected under federal law — they cannot be removed while nesting, which is precisely why timing matters. Raccoons treat a smoke shelf as a den and are strong enough to damage a damper. Squirrels frequently fall in and cannot climb back out of a slick liner. Starlings build bulky nests that block a flue thoroughly. Which animal it is changes both the legal position and the removal approach, so identification comes first.
Why late summer is the window
Once nesting is finished and the young have flown, the flue can be cleared and capped without disturbing protected wildlife. Wait until October and you are competing with the heating-season rush; act now and the chimney is clear, capped, and ready before the first cold night. If you believe there are active nestlings in the flue right now, the answer is to wait rather than to intervene, and we will tell you that plainly on the phone.
What not to do
Do not light a fire to drive an animal out. It is cruel, it is often illegal with protected species, and a panicked animal in a flue makes the blockage worse before it makes it better. Do not open the damper to look if you suspect a raccoon — the smoke shelf is directly above it. Do not pour anything down the flue. And do not assume the animal will leave on its own before winter; nests left in place are dry, resinous fuel sitting inside a chimney you are about to light.
Clearing and preventing it
Once the flue is legally clear, the nest and debris come out, the flue is swept properly, and the liner is inspected for damage caused by claws, acidic droppings, or the blockage itself. Then the flue gets capped. A stainless cap with mesh sides ends the problem permanently and keeps rain out at the same time — details on our chimney caps and crowns page. The clearing and inspection work sits under chimney sweeping and chimney inspection, with the whole list on the chimney services hub and rates on the pricing page.
Booking in Woodstock
Ace Chimney Service has served Woodstock and McHenry County for 29 years. Insured and bonded, price up front, seven days a week from 7 AM to 7 PM. Call (815) 320-0883.
Frequently asked questions
How do I know if an animal is in my chimney?
Scratching or chirping behind the firebox, fresh debris in the hearth, an unusual smell, or a fireplace that suddenly will not draft.
Are chimney swifts protected?
Yes, they are federally protected migratory birds. An active nest cannot be removed, which is why we clear and cap after nesting season.
Can I smoke an animal out?
No. It is inhumane, potentially unlawful with protected species, and it tends to leave you with a worse blockage than you started with.
Will a cap keep animals out?
A properly sized stainless cap with mesh sides is the reliable long-term fix, and it keeps rain and embers under control as well.
Is an old nest a fire hazard?
Yes. Dry twigs and leaves inside a flue are fuel in the worst possible location, and they also block the passage the smoke needs.
What if the animal has died in the flue?
The smell is unmistakable and the remains need removing before any sweeping or use of the fireplace. Call and describe what you are smelling.
Can animals damage the chimney itself?
They can bend a damper, dislodge mortar, and their droppings are acidic enough to attack a liner over time. We check for all three.
When is the best time to book this?
Late summer, after nesting finishes and before the heating-season rush, gives the shortest wait and the most useful outcome.
Published August 26, 2026