Wildfire smoke can affect Portland-area homes even when a fire is far away. This guide explains how to prepare your HVAC system and where to check current conditions. It is not a live incident report: follow local evacuation instructions and use AirNow’s wildfire resources for current smoke information.
Start With a Filter Your System Can Handle
The EPA recommends MERV 13 filtration, or the highest efficiency your system can accommodate. A higher rating is not automatically a safe drop-in upgrade. Filter dimensions, cabinet fit, blower capability, and available airflow all matter. Do not force a filter into the slot or stack filters to increase filtration.
If you are unsure what your furnace, air handler, or heat pump supports, ask for an airflow and filter assessment. Keep spare filters available and check them frequently during heavy smoke. Replace loaded filters as needed rather than relying on a universal 30-day schedule.
Understand Outdoor-Air Controls Before Smoke Arrives
Some systems have an outdoor-air intake or ventilation controls; others do not. If yours has an intake, learn the manufacturer’s smoke-event or recirculation procedure. The thermostat’s fan setting is not necessarily an outdoor-air control. Do not block combustion-air openings, flues, or safety ventilation, and do not improvise changes to equipment you cannot identify.
With a compatible high-efficiency filter installed, running the HVAC fan can increase air filtration. Confirm appropriate settings for your equipment. A mini-split’s washable screen is not a substitute for a properly selected high-efficiency air cleaner.
Use a Cleaner-Air Room When Needed
A portable air cleaner sized for the room can supplement central filtration. Choose a unit that does not intentionally produce ozone and follow its filter and operating instructions. The EPA’s clean-room guide explains how to reduce indoor smoke exposure.
Keep windows and doors closed during smoky conditions when it is safe to do so, and limit indoor particle sources such as candles and frying. If the home becomes too hot or cannot provide a safe environment, seek a safer location. Filtration does not replace evacuation orders or medical advice.
Check Ducts and Equipment Without Assuming Cleaning Is the Answer
Smoke odor alone does not prove a duct leak. Outdoor air can enter through many paths. An inspection can distinguish damaged ducts, filter bypass, ventilation settings, and other possible contributors. Duct repair and sealing should address a documented defect, not a guess based on odor.
Routine duct cleaning is not a wildfire-smoke prevention requirement. After a smoke event, evaluate any actual contamination and the equipment’s condition before deciding on cleaning. Read our guide to deciding when duct cleaning is appropriate.
A Practical Preparation Checklist
- Record your filter size and equipment-approved filtration options.
- Locate the instructions for any outdoor-air controls.
- Keep replacement filters available and check loading during smoke events.
- Check current air-quality information and local emergency alerts.
- Arrange HVAC maintenance if airflow, cooling, or controls are not working correctly.
Need Help With HVAC Preparation?
Duct Guys can evaluate HVAC operation, filter fit, airflow, and accessible ductwork in Portland-area homes. Request service or call 503-705-1176. Regular hours are Monday-Friday, 7 AM-5 PM; weekends are closed. Emergency service may be available—call to confirm.