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Smoke-day air

Smoke-day air, for homes and buildings.

What your heating and cooling system can do about wildfire smoke, what it can't, and how to get it ready before the season — in Federal Way and South King County.

Call (253) 369-3826 Schedule a pre-season check

Health first

This page is about equipment, not medicine. On smoke days, follow public-health guidance — AirNow, Puget Sound Clean Air and Public Health – Seattle & King County publish current air quality and advice. If someone in your home has heart or lung conditions, their doctor's advice comes first.

Homes with ducts

A furnace or air handler is a whole-house filter — if you let it be.

Smoke is mostly fine particles. A ducted system pulls the house's air through its filter every time the fan runs, so the filter and the fan setting decide how much it helps.

The filter: Public agencies recommend the highest-rated filter the system can handle, ideally MERV 13. Many systems can take one; some can't without changes.
The fan: Set it to On while it's smoky, so air keeps passing through the filter even when the heat or cooling isn't running.
The house: Windows and doors shut. A system can't filter the whole outdoors.
Afterwards: Change the filter after a long smoke event.

A technician sliding a new pleated filter into the filter slot of a furnace in a garage — Fitting a higher-rated filter before smoke season.

Two furnace filters side by side on a workbench, one clean white and one grey-brown after a smoke event — A filter after a week of smoke, beside a new one.

Why "can it take one?" matters

A better filter is also a denser one.

Higher-rated filters catch more particles because they resist air more. A system designed around a thin, loose filter may move much less air with a dense one — which can mean less comfort, frozen coils in summer or overheating in winter.

Before smoke season we'll check what your system can handle: the filter slot, the fan, the ductwork, and whether a deeper filter cabinet would let it take a better filter without the penalty.

Homes without ducts

Baseboards, wall heaters and ductless heat pumps.

Many houses and apartments here have no ducted system at all. Ductless heat pumps recirculate indoor air through a light filter — they'll cool the room, but they won't clean it much.

A portable HEPA air cleaner sized for the room, running where people sleep.
Keep the ductless unit's washable filters clean — they clog faster on smoky days.
Avoid anything that pulls outside air in while it's smoky.

A portable air cleaner running quietly beside the bed in a tidy bedroom, curtains drawn against a hazy day — A portable cleaner in the room that matters most.

A technician adjusting the outside-air damper linkage on the side of an open rooftop unit — Checking an economizer's outside-air damper.

Businesses

Offices, clinics, retail and restaurants.

Commercial rooftop units bring in outside air on purpose — to ventilate the space, and on mild days through the economizer to cool it for free. On smoke days that outside air is the problem.

Before the season: Check filter racks seal and can take better filters; confirm economizers can be limited.
On smoke days: Limit economizer outside air; keep the minimum ventilation the space needs unless a professional advises otherwise.
Afterwards: Replace loaded filters and return settings to normal.

Ventilation requirements depend on the space and its occupancy. We'll help you set up a smoke-day plan with those in mind — not by switching ventilation off.

Get your system ready before the smoke.

A pre-season check for homes and buildings across South King County.

Call (253) 369-3826 Schedule service