Indoor Air Quality During Wildfire Smoke: What Actually Works (and What Doesn't)
With the Gorge blanketed in smoke this week, we’ve been getting a lot of questions about what actually helps protect indoor air quality during wildfire smoke season. There’s plenty of advice out there, but the answer isn’t always as simple as closing the windows or buying a better filter.
Over nearly 30 years working in homes throughout Hood River and the Gorge, we’ve spent a lot of time looking at how heating, cooling, ventilation, ductwork, insulation, and air leakage all work together. We were formerly BPI-certified in home performance and participated in several energy-efficiency programs throughout Oregon, including Clean Energy Works Oregon. That experience taught us to look at the whole house as a system, not just the furnace or heat pump.
So when wildfire smoke rolls into the Gorge, here’s what we tell homeowners — myth by myth.
Myth #1: "Just Run the AC" Filters Out Smoke
Myth #2: Any Air Purifier Will Do
Portable air purifiers can be very effective during wildfire smoke — but sizing matters. Look for a true HEPA unit with enough clean air delivery (CADR) for the room you’re trying to protect. An undersized purifier may run constantly without moving enough filtered air to make much difference.
For a whole-home approach, we also install air-cleaning equipment designed to work directly with HVAC systems and mini-splits, including the Aerus Pure & Clean. Depending on the home and the people living in it, we may recommend combining a portable HEPA unit with whole-home equipment rather than relying on one device alone. These systems do require some upkeep — the bulbs and active cells need replacement every few years.
Myth #3: Closing the Windows Is Enough
Closing up the house helps, but it’s not the whole story. If you’re getting smoky or musty smells, duct leakage is one of the first things worth investigating. Leaky return ducts can pull contaminated air from attics, crawlspaces, and other unconditioned areas and distribute it through the house. That’s why we usually look for leakage and pressure problems before recommending duct cleaning. As a home performance contractor, we always start by looking at the “lid” of the home — the attic and building envelope — because that’s usually where the biggest leaks are, long before we ever get to the furnace.
Myth #4: A Higher MERV Filter Is a Simple Upgrade
This one’s understandable — on paper it looks simple: buy a MERV 13 filter, drop it in, done. In practice, we often don’t know how a home’s ductwork was installed or what static pressure the system was designed for. Pushing air through a denser filter than the system was sized for can choke airflow, strain the blower motor, or in extreme cases cause coil icing. This is one of the real advantages of an electronic air cleaner like the AccuClean Whole-Home Air Cleaner, which we install: it uses an electric charge to capture particles rather than relying purely on dense filter media, so it doesn’t create the same resistance to airflow. We hear that a basic filter upgrade is “cheaper” — and it is — but you generally can’t safely install the same MERV rating in a standard filter slot without risking static pressure problems. AccuClean gets you similar filtration performance without asking your blower to fight it.
How to Protect Indoor Air Quality During Wildfire Smoke
- Start with the building envelope, not the equipment. Air sealing and insulation — the “lid” of the home — reduce how much smoke gets in before you ever touch the HVAC system.
- Address duct leakage before duct cleaning. Sealing leaky return ducts stops smoke from being drawn into your supply air.
- Know whether your system brings in outdoor air. Some homes have mechanical ventilation or outdoor-air intakes. During heavy smoke, those may need to be adjusted temporarily — but don’t just shut equipment off without understanding how your home is ventilated.
- Use MERV 13 filtration where your system supports it, and have a technician confirm static pressure before going higher.
- Consider a whole-home electronic air cleaner (like AccuClean) if a standard filter upgrade isn’t safe for your ductwork.
- Add a properly sized air purifier or scrubber — a true-HEPA portable for a single room, or equipment like the Aerus Pure & Clean installed on ductwork or mini-splits for broader coverage — especially for allergy or smoke-sensitive households.
- Create a cleaner-air room during severe smoke. Choose a bedroom or other room you spend a lot of time in, keep windows and doors closed, and run a properly sized HEPA purifier there. Even if you can’t filter the whole house perfectly, cutting exposure in one occupied space helps.
- Don’t guess. Get a consult from a qualified HVAC technician, ideally one trained in whole-home building science.
If you’re not sure where your home stands, we’re happy to come take a look and talk through what actually makes sense for your home. Sometimes the answer is better filtration, sometimes it’s duct or air sealing, and sometimes what you already have is perfectly adequate — we’ve been doing this in the Gorge for almost 30 years.
FAQ
Q: What MERV rating should I use during wildfire smoke season?
A: MERV 13 is the practical target for most homes — it captures the fine particulate in wildfire smoke without the airflow problems you can run into at MERV 16. Always confirm with a technician that your system can handle the increased static pressure.
Q: Do I need to clean my ducts before smoke season?
A: Usually not. If you’re getting smoky or musty smells, duct leakage is one of the first things worth investigating. Leaky return ducts can pull contaminated air from attics, crawlspaces, and other unconditioned areas into the system. That’s why we typically check for leakage and pressure problems before recommending duct cleaning.
Q: Will a portable air purifier protect my whole house?
A: A properly sized, true-HEPA portable purifier can be very effective in the room it’s placed in — sizing (CADR) for the room is what matters most. It won’t treat the whole house on its own, though, which is why we often combine a portable unit with whole-home equipment like an air scrubber or electronic air cleaner for full coverage.
Q: Does closing my windows stop my HVAC system from bringing in outside air?
A: Not necessarily. Some homes have mechanical ventilation or outdoor-air intakes as part of the HVAC system, and closing windows alone doesn’t affect those. During heavy smoke, it’s worth having a technician check whether your system is intentionally bringing in outside air and whether it should be adjusted.
Q: Can I just install the highest MERV filter I can find?
A: Not safely, in most homes. We often don’t know how a home’s ductwork was installed or what static pressure it was designed for, so jumping straight to a very high MERV filter can strain your system. An electronic air cleaner like AccuClean gets similar filtration without that airflow resistance.
Q: What’s an air scrubber, and do I need one?
A: An air scrubber actively treats air as it moves through your ductwork, a mini-split head, or a portable unit, rather than just filtering it. We install the Aerus Pure & Clean for this. It’s especially worth considering if someone in your home has allergies or is sensitive to smoke — we often pair it with an electronic air cleaner for extra coverage.
— The McDowell & Son Crew