Wildfire-smoke indoor air quality: a Spokane homeowner\u2019s playbook
Spokane\u2019s air quality during late-summer smoke weeks has gotten measurably worse over the last decade. A typical August used to mean maybe 2\u20133 days of moderate smoke. Now it\u2019s 2\u20133 weeks of \u2018unhealthy\u2019 to \u2018hazardous\u2019 air. Here\u2019s what Spokane homeowners are actually doing to keep their homes livable.
Marisa K.
Owner / Dispatch Lead, NATE-certified · August 30, 2025 · 10 min read
Quick answer
Spokane wildfire-smoke IAQ strategy: (1) MERV-13 whole-home filtration, (2) fresh-air ventilation with intake-side MERV-13, (3) positive pressure mode (if your HVAC supports it), (4) portable HEPA air purifier in the bedroom, (5) IQAir-style whole-home air purifier, (6) tight envelope (caulk + weatherstrip), (7) keep windows closed on bad-air days, (8) check Spokane Clean Air Agency air-quality readings twice daily during smoke season.
- Spokane wildfire season: July–October, peaking late August.
- MERV-13 captures 50%+ of PM2.5 (wildfire smoke particles).
- Portable HEPA purifier: $200–$600.
Spokane smoke weeks are getting worse. Here\u2019s how to keep your home livable without making your AC work overtime — straight from IAQ installs we\u2019ve done across South Hill and Five Mile Prairie.
Why Spokane smoke is worse than it used to be
Three things changed: (1) more frequent and larger fires east of the Cascades, (2) warmer summers that extend fire season into September and October, (3) Spokane’s geography — we’re in a valley that traps smoke when there’s no wind.
The result: smoke weeks that used to last a few days now last weeks. PM2.5 levels that used to peak at 100–150 (unhealthy for sensitive groups) now regularly exceed 250 (very unhealthy) and occasionally exceed 500 (hazardous).
For context: the EPA’s 24-hour ‘unhealthy’ threshold is 35. We’re seeing 7–14x that during bad smoke weeks.
The four-stage playbook
Most Spokane homeowners go through four stages of IAQ upgrades as they experience smoke weeks. Here they are, in order of cost-effectiveness.
Stage 1: MERV-13 retrofit ($349–$649 installed). If your HVAC was built after 2010, we can usually retrofit a 4” MERV-13 media filter cabinet without replacing equipment. Captures ~85% of PM2.5.
Stage 2: Fresh-air ventilation ($2,800–$4,800 installed). For tight modern homes. HRV or ERV brings in filtered outside air while recovering heating/cooling energy. Critical for tight homes.
Stage 3: IQAir-style whole-home air purifier ($1,400–$2,800 installed). HEPA + carbon filtration for severe smoke sensitivity, allergies, or asthma. Captures 99.97% of PM2.5 and most VOCs.
Stage 4: Heat pump + tight envelope ($14,800+). Modern heat pumps filter continuously during smoke weeks. The combination of tight envelope + MERV-13 + heat pump is the gold standard for Spokane homes.
What actually works (and what doesn’t)
Works: MERV-13 retrofit, fresh-air ventilation, whole-home air purifier, tight envelope, smart thermostat with fan-only mode, IQAir standalone units in bedrooms.
Mostly works: standalone HEPA air purifiers in main living areas, DIY box fan + MERV-13 filter (Corsi-Rosenthal boxes — surprisingly effective for $50).
Doesn’t work well: leaving windows closed without filtration, running AC without a MERV filter upgrade, ozone generators (illegal in some states for a reason — ozone is harmful to lungs).
Don’t bother: cheap furnace filter ‘upgrades’ that aren’t actually MERV-13. Check the actual rating — most ’allergy’ filters are MERV-8 or MERV-10.
How to know it’s working
Buy a PM2.5 monitor (~$50–$200 on Amazon). Place it in your main living area. Run your system with MERV-13 filtration. Compare indoor vs outdoor readings.
If your system is working well, indoor PM2.5 will be 70–90% lower than outdoor levels during smoke weeks. Most Spokane homes with MERV-13 + tight envelope hit 80%+ reduction.
If indoor readings are close to outdoor readings, your envelope isn’t tight enough, your filter is overloaded, or your system isn’t running continuously.
The cost-benefit math
For a typical Spokane family with kids or elderly relatives, the IAQ upgrades pay back in reduced medical costs (asthma exacerbations, ER visits), reduced missed work/school days, and quality-of-life improvements that are hard to put a price on.
We’ve seen families who evacuated Spokane every August for years because of smoke. After a $1,800 IAQ retrofit, they stayed home for the entire 2024 smoke season.
If you have severe smoke sensitivity or asthma, this isn’t optional. It’s a quality-of-life upgrade that pays back faster than almost any other home improvement.
If you\u2019re considering IAQ upgrades for your Spokane home, we\u2019ll come out, measure your current indoor air quality, and design a staged improvement plan. Most homes start at $349 for the MERV-13 retrofit and go up from there based on your needs and budget.