By Johnathan Mason, Ace Chimney Service.
A chimney balloon or fireplace plug can cut the cold draft from a fireplace you are not using, but it only works if it fits the opening and gets removed every single time before a fire. For a lot of Cary homes with an older, poorly sealing damper, a plug is a reasonable winter stopgap. It is not a repair, and it creates one new risk you have to manage.
What these products are
They are removable seals that block airflow up the flue when the fireplace is idle. The common types are an inflatable pillow pushed up into the throat just below the damper, a firm foam block cut to fit the same space, and a flat cover that closes off the fireplace opening itself, often held by magnets on a metal surround. All three aim at the same thing: a column of warm indoor air escaping up the chimney all winter, and cold air falling back down.
When a plug makes sense
A plug is most useful when the damper leaks and the fireplace sits unused for long stretches. Throat dampers in older homes warp, rust, or stop closing fully, and a gap you can feel with your hand on a cold night is heat you are paying for. If you light a fire only a few times a season, a plug closes that gap cheaply until the damper itself is dealt with.
If you burn often, a plug becomes a chore, and one you will eventually skip. That is the point where a real repair is worth more than a workaround.
The one rule that matters
Never light the fireplace with the plug in place. With the flue blocked, smoke has nowhere to go but into the room, and a pillow or foam block left above a fire can scorch or burn. Most products include a hanging tag meant to be seen from the hearth. Keep it visible, and make removal part of the routine: plug out, damper open, then kindling.
If your household has more than one person who lights fires, everyone needs to know it is there.
When not to use one at all
Gas fireplaces and gas logs are the big exception. A vented gas appliance needs an open path for its exhaust, and some fireplaces are fitted with a damper clamp so the damper can never close fully. Do not plug a flue that serves any gas appliance, including one with a standing pilot. For those, a gas fireplace service visit is the right place to talk about heat loss.
A plug also will not solve rain coming down the flue, animals getting in, or a damaged crown. Those are problems at the top of the chimney, handled with a cap or crown work, not a seal at the bottom.
Getting the fit right
A loose plug does little, and an oversized one can be forced up where it tears or gets stuck. Measure the throat or opening carefully before buying, and check that the plug sits flat without gaps at the corners. Pull it out now and then to look for soot, moisture, or damage, since a wet or blackened plug is telling you something about the flue above it.
The longer-term fix
If you are plugging the fireplace every winter because the damper will not seal, a top-sealing damper or a damper repair usually ends the problem for good. We look at the damper, the smoke chamber, and the flue during a chimney inspection, which NFPA 211, the standard we work to, calls for once a year whether or not the fireplace gets much use. You can see every option on our chimney services page.
Ace Chimney Service brings twenty-nine years of experience, is insured and bonded, and quotes the price up front. Call (815) 320-0883, seven days a week from 7 AM to 7 PM, anywhere in Crystal Lake and McHenry County.
Frequently asked questions
Does a chimney balloon really stop drafts?
When it fits snugly below the damper, it greatly reduces air moving up and down the flue. Results depend on fit; a balloon that is too small for the throat leaves gaps at the edges.
What happens if I forget and light a fire with it in?
Put the fire out right away, open windows, and let the room clear. Smoke will pour into the room and the plug can be damaged. Have the fireplace looked at before using it again.
Can I use a plug with gas logs?
No. Any vented gas appliance needs a clear exhaust path at all times. Blocking it can push combustion gases into the house.
Is a fireplace plug better than fixing the damper?
It is cheaper up front, but it is a workaround. If the fireplace gets regular use, repairing or upgrading the damper is the more reliable answer.
Will a plug keep animals out of the chimney?
It may stop an animal reaching the room, but it does nothing to keep one out of the flue. A properly fitted chimney cap is what keeps birds and raccoons from moving in.
Do magnetic fireplace covers work on every fireplace?
Only where there is a flat steel surface around the opening for the magnets to hold. Brick or stone surrounds need a different style of cover.
Should I close the damper with a plug installed?
Close it as far as it will go, then fit the plug below it. The two together seal better than either one alone.
Can I install a plug myself?
Yes, most are made for homeowners. Wear a mask, since soot tends to fall when you reach into the throat, and see our DIY chimney care page for safe basics.
Published: October 24, 2026