Wildfire smoke and your windows

Montana’s air is “occasionally affected by smoke from wildfires during the summer months,” in the words of the state Department of Environmental Quality, and the fire does not have to be close. The department notes that prevailing weather “often transport[s] smoke into Montana from fires burning in California, Idaho, Oregon, Washington and Canada.”

What comes out of smoke is soot and ash. Near a fire, FEMA says it “may be visible on exterior siding and/or windows.” Smoke from far away leaves less, but whatever settles ends up on the glass and in the screens.

Do not wipe it off dry

Ash is grit. Dragged across glass on a dry cloth or a squeegee, it can leave fine scratches, which is why the glass industry’s cleaning guidance starts with soaking the glass: “sufficient water will help prevent abrasive particles from being trapped between the glass and the cleaning tools.” The EPA gives the same advice for your lungs: “Avoid dry sweeping or dusting.”

How to clean it

1. For more than a light dusting, wear an N95 or P100 respirator and gloves. The EPA says surgical masks and one-strap dust masks “will not protect your lungs,” and that wet ash can irritate skin.
2. Mist the glass and frame to settle the ash, using as little water as you can, and do not wash ash into a storm drain.
3. Wash with a mild mix of dish soap and water on a microfiber cloth, as FEMA’s smoke-damage guide describes, rinsing the cloth often.
4. Take the screens out and rinse them gently. They catch ash the way they catch dust.
5. No pressure washer: Andersen says pressurized tools “may cause damage and is not recommended.”

When

Wait until the smoke has cleared, or the glass just collects the next layer. Montana’s Department of Natural Resources and Conservation calls May through September “the core of wildfire season for Montana,” so in a smoky year the fall cleaning is the one that counts. The best time of year to wash windows in Bozeman has the rest of the calendar.

When to call us

Upper-floor glass, a heavy layer of ash, or glass that still looks hazy after a careful wash. A haze that will not come off may be something else, such as hard-water spotting that needs its own treatment. How to tell, and what to do about it.