Chimney Smells in Summer: How to Fix Lingering Odors in Lynnwood’s Older Homes

By David Chimney Team · Updated July 30, 2026

Summer chimney odors are caused by creosote deposits mixing with humidity and changes in air pressure, pushing acidic smells down into your home. To fix chimney smells in summer, remove the creosote source through sweeping and improve draft or waterproofing to prevent moisture absorption in the masonry.

Why High Humidity Activates Creosote Scents in Lynnwood Chimneys

In the maritime climate of the Puget Sound, our warm days are often paired with significant humidity or heavy morning dew. When you ask, "why does my chimney smell in summer," you are experiencing a chemical reaction involving creosote. Creosote is an oily, acidic byproduct of wood combustion that coats your flue tiles. While it is dormant and stable during the dry winter burning season, it becomes highly odorous when exposed to moisture. The humidity common in Lynnwood, especially in neighborhoods near the wetlands or lake systems, causes this residue to release a pungent, campfire-like odor. Because creosote is hygroscopic, meaning it absorbs moisture from the air, the damp summer air essentially rehydrates the soot, allowing those volatile organic compounds to travel down the chimney stack and into your living room. Addressing this requires removing the fuel source; you can learn more about this process in our complete guide to chimney sweeping.

Protecting Your Older Masonry from Absorbing Moisture

Older homes in the Lynnwood area, particularly those built in the mid-20th century with standard brick chimneys, face specific challenges due to the porosity of aging masonry. Over decades, the mortar joints between bricks develop hairline cracks, and the bricks themselves become more porous, acting like a sponge. When rain falls—which happens frequently here even in July—water soaks into the chimney structure. This moisture combines with the creosote inside the flue to amplify the smell significantly. It is not just a surface odor; it is a sign that water is deteriorating your chimney's structural integrity. If you live in an established area like Alderwood Manor, you may notice this issue is more pronounced in homes that haven't had masonry maintenance recently. This degradation often leads to the need for specialized repairs detailed in our guide to chimney masonry repair & tuckpointing. Effective waterproofing involves applying a breathable masonry sealant that stops liquid water from entering while allowing water vapor already inside the chimney to escape, preventing the damp conditions that cause odors.

Reversing the Draft: Why Air Comes Down During Summer

Air pressure dynamics in your home change drastically between winter and summer, playing a major role in why fireplace smells appear only when the fireplace is not in use. During winter, the hot air inside the chimney rises rapidly, creating a strong updraft that pulls smoke up and out. However, during a typical Lynnwood summer, if your home is air-conditioned or cooler than the outside temperature, the air inside the chimney becomes heavy and dense. This causes a 'stack effect' reversal, where cool air sinks down the flue and pushes the smelly air into the hearth. This negative pressure is exacerbated by air-tight modern windows and doors, which prevent replacement air from entering the home to push the draft back up. To mitigate this, you need to either provide a source of combustion air or restrict the airflow at the chimney top. Top-sealing dampers are excellent for this, acting as a chimney door that seals shut when the fireplace is idle.

Restoring Flue Integrity to Prevent Trapped Odors

A critical factor in persistent summer stench is the condition of the flue liner, especially in vintage Lynnwood residences. Many older homes were constructed with unlined masonry chimneys or clay tile liners that have shifted and cracked over decades due to the region's wet winters and soil settlement. When these liners are damaged, creosote soot permeates the porous masonry joints behind the tiles. Even after a sweep, the smell remains because the odor is embedded deep within the chimney structure itself, rather than just sitting on the surface. We often see this in Mountlake Terrace and surrounding neighborhoods where housing stock is similar. The solution is often relining the chimney with a stainless steel liner, which creates a smooth, non-porous barrier that seals the old masonry and isolates the odors. You can explore the differences between repair approaches in our article on repairing vs. replacing a chimney. A properly sized liner also improves draft year-round, reducing the likelihood of downdrafts carrying smells into your home.

Practical Steps to Eliminate the Stench for Good

To effectively tackle chimney smells in summer, you must take a multi-pronged approach that addresses cleanliness, airflow, and water intrusion. First, a professional sweeping is mandatory; if there is no fuel (creosote), there is significantly less smell for the humidity to activate. We follow the rigorous standards set by ((the Chimney Safety Institute of America (CSIA)|https://www.csia.org/)) to ensure the flue is down to the bare masonry. Next, inspect the chimney cap. If it is missing or damaged, rain is freely entering the flue, which is the primary catalyst for the odor. Installing a cap also prevents rodents, which are a completely different and often worse source of summer smells. Finally, consider installing a top-sealing damper. This provides a tight seal at the top of the flue, unlike a traditional throat damper which is metal-to-metal and rarely airtight. If you are unsure of the source of the smell, our about our team and credentials page explains how we use video scanning technology to spot hidden issues. For specific help assessing your situation, please request a free estimate / contact us.

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