Smoke events have become a regular part of Washington summers on both sides of the Cascades, and they create a direct conflict with the night-flushing approach that otherwise keeps homes cool.
Prepare before the season
Everything here is easier to arrange in June than during an event, when air cleaners sell out and HVAC contractors are busy.
Check what filter your system can take. Higher-rated filters capture finer particles, but they also restrict airflow. A filter too restrictive for your equipment reduces performance and can damage it over time. Ask an HVAC contractor what your specific system handles rather than buying the highest rating available.
Find the fresh-air intake, if you have one. Some systems draw outside air deliberately. Knowing whether yours does and how to close it matters during an event.
Buy air cleaners early. Sized for the rooms where you spend most time. They sell out when smoke arrives.
Check seals. Weatherstripping and caulking that keep heat in during winter also keep smoke out in summer. Gaps around doors and windows work against you in both directions.
During an event
Keep windows and doors closed, including at night. This is the hard part, because it removes the night-flushing that keeps a house cool, and smoke events often coincide with heat.
If you have cooling, run it on recirculate rather than drawing outside air. If you do not, you are balancing heat against smoke, and that balance depends on how hot it actually is and who is in the house.
Avoid adding indoor particles. Candles, incense, frying and vacuuming without a good filter all put more into air that is already compromised.
The clean room approach
Rather than treating the whole house, choose one room — usually a bedroom — and concentrate on keeping it cleanest. A portable air cleaner sized for that room, doors kept closed, gaps sealed.
This is a practical approach for households with anyone who has asthma or another respiratory condition, and it is far more achievable than filtering an entire house.
Filters and what they do
Wildfire smoke particles are very fine, which is why ordinary filters do little. Filters need a high enough rating to capture fine particulate to be useful for this purpose.
The trade-off is airflow. This is why checking with an HVAC contractor matters — the right answer is the highest rating your system can handle without restriction, and that number is specific to your equipment.
Portable air cleaners
Effective when sized properly for the room. An undersized unit in a large space achieves little.
Check the rated room size rather than assuming, and remember that a cleaner needs its filters replaced — a unit running on saturated filters is doing considerably less than its owner believes.
After the event
Once air quality improves, ventilate thoroughly to clear whatever accumulated indoors. Replace HVAC filters, which will have loaded heavily. Replace portable air cleaner filters if they have run continuously.
Surfaces may hold residue, and cleaning helps if the smell persists.
The longer-term question
If smoke events are affecting your household repeatedly, it is worth discussing filtration as part of any HVAC work rather than as a seasonal add-on. A system specified with filtration in mind performs better than one adapted to it afterwards.