A chimney plug can help block drafts, odors, noise, and debris when a fireplace is not in use. The right choice depends on the flue’s shape and measurements: the inflatable Door plug is best for many masonry fireplaces, while the Flueblocker options suit specific round or rectangular openings. A separate Door model is designed for many metal, zero-clearance fireplaces. Measure the opening before choosing, and remove any plug before lighting a fire.
| Product | Best for | Fit or material |
|---|---|---|
| Door Large Fireplace Draft Stopper | Many masonry fireplaces | Rectangular damper openings up to 38 x 16 inches |
| Flueblocker Round Plug | Round flues | 8–9-inch openings |
| Rectangular Chimney Flue Plug | Smaller rectangular flues | 8 x 32 inches or smaller, subject to fit conditions |
| Door Round Chimney Draftstopper | Many metal fireplaces | Round; exact dimensions are not provided |
| Flueblocker 13 x 35 | Large rectangular flues | Up to 13 x 35 inches |
Door Large Fireplace Draft Stopper
Best for: Owners of brick or masonry fireplaces with a rectangular damper opening up to 38 x 16 inches. This is an inflatable chimney plug rather than a wool or felt insert. It installs below the damper, and its telescoping pole supports the pillow during placement.
The listed features say the plug is made of polyurethane and is intended to help reduce energy loss, downdrafts, odors, toxins, noise, and insects. Installation is described as quick and clean. Its broad stated fit range makes it a practical option for buyers whose masonry fireplace dimensions fall within the listed limit.
Why it was selected: It directly addresses searches for a balloon-style fireplace plug and provides a stated maximum size for many rectangular masonry fireplaces. Choose this if you want an inflatable plug and your fireplace matches the listed construction and dimensions.
Limitation: The product is specified for brick or masonry fireplaces with rectangular dampers, so it is not the best choice for a round flue or a metal, zero-clearance fireplace. Measure the opening rather than relying on “fits most.”
Flueblocker Plug For 8–9-Inch Round Flues
Best for: People with an 8- or 9-inch round chimney flue who want a pressure-fit plug instead of an inflatable balloon. The listed product diameter is 10 inches, providing a compression-based fit in the specified opening range.
The wool plug is placed directly in the flue above the firebox, so its installation does not depend on the fireplace damper working. The product description says it can help block drafts, odors, noise, and falling debris. It requires no tools to install, and the edges can be trimmed with scissors for fit adjustment.
The listing describes it as suitable for year-round use in inactive fireplaces and wood stoves. It states that seasonal use can allow the wool plug to last more than seven years, while continuous installation may allow it to last indefinitely. These are product claims, not a substitute for checking the plug periodically.
Why it was selected: It offers a clearly defined option for a round flue and a broken, stuck, or missing damper. Limitation: It is not a general-purpose choice for rectangular flues; confirm the opening is within the listed round size range.
Rectangular Chimney Flue Plug
Best for: Buyers with a rectangular flue measuring 8 x 32 inches or smaller, provided the damper is slightly larger than the flue opening. The plug measures 9 x 33 inches and has three sewn-in loops that allow trimming for a closer fit.
This model uses high-grade, fire-resistant felt. Its dense mat is described as blocking airflow, drafts, odors, noise, and debris, while helping keep warm air in during winter and cooler air in during summer. A telescopic metal pole extends from 16 to 60 inches to help position the plug.
Why it was selected: It gives shoppers a non-inflatable option for a specified rectangular flue size and includes an adjustable pole for placement. Choose it if your opening and damper relationship match the listing’s fit instructions.
Limitation: The listed size is not suitable for every rectangular fireplace. The product directions call for a damper slightly larger than the flue opening, so check both measurements before ordering.
Door Round Chimney Draftstopper
Best for: Owners of metal, zero-clearance fireplaces looking for a round chimney seal. The product name specifically identifies these fireplace types, distinguishing it from the masonry-focused inflatable plug above.
The available features describe the stopper as energy efficient, intended to improve home comfort, and designed to seal the chimney. The listing does not provide a diameter, material, installation method, or detailed fit range in the supplied product information. Buyers should therefore verify the dimensions and installation details on the product page before selecting it.
Why it was selected: It is the only option in this group specifically identified for most metal, zero-clearance fireplaces. Choose this if your fireplace matches that type and the product’s current sizing information confirms a fit.
Limitation: Exact dimensions are not included in the provided details, so it is harder to compare fit confidently. Avoid assuming that “round” means it will fit every round chimney.
Flueblocker For 13 x 35-Inch Chimneys
Best for: Homeowners with a large rectangular flue up to 13 x 35 inches who prefer a reusable wool insert. Its actual dimensions are 14 x 36 inches to create a pressure fit, and the manufacturer advises choosing a plug at least one inch larger than each flue dimension.
The plug is made from 100% Herdwick wool and weighs 2.6 pounds. The listing describes it as holding its shape and being reusable for more than 10 years of seasonal installation and removal cycles. The edges can be trimmed with scissors for a custom fit. It is designed for rectangular flues only.
The product is intended to help block drafts, odors, noise, and debris and retain heat when the fireplace is inactive. The listing also states that it complies with IECC 2009 section 402.4.2 as a prescriptive insulation product.
Why it was selected: Its larger stated dimensions make it a better match than the round Flueblocker for large rectangular openings. Limitation: It is not designed for round flues, and accurate measurements are essential for a pressure fit.
Buying Guide: How To Choose A Fireplace Chimney Plug
What should you measure before buying?
Measure the inside width and depth of a rectangular flue, or the inside diameter of a round flue. Measure at the opening where the plug will sit, not merely the visible fireplace surround. Product dimensions may be larger than the stated flue size when a pressure fit is intended. Follow the specific product’s sizing directions and check whether its measurement refers to the plug or the opening.
For the Door large inflatable model, compare your masonry fireplace’s rectangular damper opening with the stated maximum of 38 x 16 inches. For the rectangular felt plug, check the 8 x 32-inch limit and its requirement that the damper be slightly larger than the flue. For the wool models, match both shape and dimensions before considering trimming.
Should you choose an inflatable balloon or a wool plug?
An inflatable plug is a direct match for buyers specifically seeking a chimney balloon. The Door masonry model is intended for rectangular damper openings and includes a telescoping support pole. A wool plug is a non-inflatable alternative that pressure-fits into a flue. The round Flueblocker is sized for 8- to 9-inch openings, while the larger Flueblocker is for rectangular openings up to 13 x 35 inches.
These options are not interchangeable just because they all block a chimney. Shape, fireplace construction, and fit determine which style is appropriate. A plug that is too small may not seal well; one that is too large may not install as directed.
Does the damper need to work?
Some plug types are installed independently of the damper. The round Flueblocker is described as sitting directly in the flue, so its fit does not depend on the damper mechanism. The rectangular felt product, by contrast, includes a fit condition about the damper being slightly larger than the flue opening. Check each product’s instructions rather than assuming every plug works with every damper condition.
Which material and installation approach fits your needs?
Inflatable plugs use an air-filled pillow-style design, while the supplied alternatives include wool and fire-resistant felt. Consider how the product is placed and removed, whether a pole is included, and whether trimming is permitted. A telescoping pole may help reach a higher opening. A pressure-fit wool plug may be attractive to buyers who want a reusable insert, but it still requires the correct dimensions and flue shape.
When should a chimney plug be removed?
Use a chimney plug only when the fireplace is inactive. Remove it before lighting a fire, and follow the product’s complete safety and installation instructions. Keep a clear reminder near the fireplace so the plug is not forgotten. Do not use a plug to compensate for an unsafe chimney, damaged firebox, or ventilation problem; consult a qualified chimney professional if the condition of the fireplace is uncertain.
Also consider whether a chimney is shared with another appliance or serves a venting purpose. Do not block a flue that must remain open for another appliance. If you are unsure what the flue serves, get professional guidance before installing a stopper.
Frequently Asked Questions
Can I leave a chimney balloon in all winter?
A plug can remain in place while a fireplace is inactive if its instructions allow it. The Door inflatable model is intended to block drafts when not in use. Remove it before lighting a fire, and check it regularly for secure placement and any change in condition.
How do I know whether I need a round or rectangular plug?
Look at the flue opening above the firebox and measure its shape and dimensions. Round openings need a plug specified for a round flue; rectangular openings need a rectangular model sized for that opening. Do not choose based only on the shape of the fireplace opening in the room.
Will a chimney plug work if my damper is broken?
Some products are positioned directly in the flue and do not rely on the damper. The round Flueblocker listing specifically says it works regardless of damper condition. Other models may have separate fit requirements, so review their instructions before purchase.
Can I trim a chimney plug to make it fit?
Trimming is described for both Flueblocker products and the rectangular felt plug, but it is not stated for every product. Follow the specific product directions and do not trim an inflatable plug unless its instructions expressly permit it.
Can I block a chimney that is used by a stove or another appliance?
Do not block a flue that an operating appliance needs for exhaust or ventilation. Confirm what the flue serves before installing any stopper. If you cannot identify its purpose, ask a qualified chimney professional.