Wildfire Smoke Season and Your Home's Air

Every August, our phones ring off the hook. The sky turns orange, the AQI hits "hazardous," and suddenly everyone in Enumclaw is thinking about indoor air quality for the first time since last August. Here's what actually works, what doesn't, and what you can do before the smoke rolls in.

This isn't going away

Let's start with the uncomfortable truth: wildfire smoke in Western Washington isn't an anomaly anymore. It's seasonal. The summers of 2020, 2021, 2022, and 2024 all brought extended periods of hazardous air quality to our area. The Bolt Creek fire, the BC wildfires, eastern Washington burns — the smoke doesn't care which side of the Cascades you live on.

If you don't have a plan for managing your indoor air when outdoor air becomes unsafe, you're going to keep having the same panicked August every year.

Your HVAC system is already your first line of defense

If you have central heating and cooling (a furnace, heat pump, or air handler with ductwork), your home's air is already being filtered every time the system runs. Air gets pulled through a return duct, passes through a filter, gets heated or cooled, and circulates back into your rooms.

The question is: what filter are you using, and when did you last change it?

The filter matters more than you think

Filters are rated on the MERV scale (Minimum Efficiency Reporting Value). Higher MERV = smaller particles captured.

• MERV 1–4: The cheap fiberglass filters from the hardware store. These protect your equipment from large debris (dust bunnies, pet hair). They do almost nothing for air quality. Smoke particles blow right through.
• MERV 8: The standard pleated filter. Catches most dust and pollen. Better, but still lets most smoke particles through.
• MERV 11–13: This is the sweet spot for residential systems. These filters capture a meaningful percentage of fine particulate matter, including much of the PM2.5 that makes wildfire smoke harmful. Most residential HVAC systems can handle a MERV 13 filter without airflow issues.
• MERV 14–16 (HEPA territory): Catches nearly everything, but most residential systems aren't designed for this level of restriction. Forcing a HEPA filter into a standard furnace can reduce airflow to the point where the system overheats or freezes up. Don't do this without talking to a technician first.

Our recommendation: Run a MERV 13 filter year-round and change it more frequently during smoke season (every 2–3 weeks instead of every 3 months). It's one of the cheapest, most effective things you can do.

Run your fan during smoke events (even if you don't need heating or cooling)

Most thermostats have a fan setting separate from heating/cooling. Set it to "ON" instead of "AUTO" during smoke events. This circulates your home's air through the filter continuously, even when the system isn't actively heating or cooling. It uses a small amount of electricity but provides ongoing filtration.

What about standalone air purifiers?

They work — with caveats.

Portable HEPA air purifiers (brands like Austin Air, Blueair, or IQAir) are effective for individual rooms. A good one can clean the air in a bedroom or living room within 30–60 minutes. During smoke events, running one in the bedroom at night makes a real difference in sleep quality.

The limitation: They only clean the room they're in. A portable purifier in your bedroom doesn't help your kitchen, your kids' rooms, or your living room. To protect the whole house, you'd need one per room — which gets expensive and noisy.

Whole-home air purifiers connect directly to your HVAC system and treat every cubic foot of air in your home as it circulates. These are more effective than portables for whole-house coverage and run silently. We install several options, including electronic air cleaners and UV germicidal systems that address both particulate and biological contaminants (mold, bacteria, viruses — not just smoke).

The "box fan with a furnace filter" hack

You've seen it on social media. Tape a MERV 13 filter to the back of a box fan. Does it work?

Kind of. It's better than nothing during an emergency, and the Puget Sound Clean Air Agency has actually endorsed it as a temporary measure. But it's loud, it's ugly, it's sitting in the middle of your living room, and it's filtering a fraction of the air volume that your HVAC system moves. Think of it as the "I forgot to prepare" backup plan, not a real strategy.

What doesn't work

• Opening windows to "air out" the house during smoke events. This is the opposite of what you want. Keep the house sealed. Run the HVAC fan for filtration.
• Running your AC in "fresh air" mode (if your system has one). Some systems have an outside air intake. During smoke events, close it or switch to recirculation mode.
• Burning candles or incense "to cover the smell." You're adding particulate matter to already bad air. Don't.
• Assuming the smoke isn't that bad because it doesn't look that bad. PM2.5 particles are invisible. The AQI can be hazardous even when the sky looks only mildly hazy.

The pre-smoke-season checklist

Don't wait until August. Do this in June or July:

1. Replace your HVAC filter with a MERV 11 or 13 (check your system's specs first — or ask us).
2. Buy a second filter so you have a replacement ready when the first one loads up during smoke season.
3. Schedule a maintenance checkup to make sure your system is running efficiently. A system that's struggling mechanically won't filter well either.
4. Consider a whole-home air purification upgrade if you haven't already. This is especially important for households with asthma, allergies, elderly family members, or young children.
5. Test your thermostat's fan-only mode so you know how to use it when the smoke arrives.

The bigger picture

Indoor air quality isn't just a smoke-season issue. Dust, pet dander, pollen, mold spores, and volatile organic compounds (VOCs from cleaning products and building materials) are year-round concerns. The same systems and habits that protect you during wildfire season also make your home healthier the other 10 months of the year.

If you're curious about your home's air quality or want to explore filtration options, we're happy to take a look. We can assess your current setup, recommend upgrades that fit your system and budget, and make sure your home is ready before the smoke decides to visit again.