Every winter the Salt Lake Valley does the same thing. A layer of warm air settles over the top of the valley, cold air gets trapped underneath it, and everything we put into that cold air stays there. The mountains hold it in place. It can sit for days or weeks until a storm finally scours it out.
During an inversion, the fine particulate in the valley air, the fraction known as PM2.5, climbs to levels that get discussed on the news and drive advisories from the state.
What gets discussed far less is that PM2.5 does not stop at your front door, and one of the places it settles is your bed.
Why indoor air is not a solution
PM2.5 means particles under 2.5 micrometers. For scale, a human hair is somewhere around 70 micrometers across. These particles are small enough to stay suspended in air for long stretches and small enough to move through gaps that feel completely sealed.
Weatherstripping that has aged, the gap under an exterior door, the dryer vent, the attic hatch. A house is not an airtight container, and during a multi-day inversion the outdoor concentration is high enough and sustained enough that indoor levels follow.
Your furnace is the other route. It pulls air through a return and pushes it through every room, so whatever the filter does not catch gets distributed and redistributed all winter.
Particles that fine settle slowly and land on horizontal surfaces. Your bed is the largest one in the house, it is made of fabric that holds what lands on it, and you spend eight hours a night with your face pressed into it, breathing.
What to do during inversion season
The furnace filter is the highest-value item on this list. Check it monthly through the winter rather than on the schedule on the box. A loaded filter stops filtering and starts restricting airflow, which makes the system pull harder around the filter edges and defeats it entirely.
Upgrade one step, not three. A filter too restrictive for your system strains the blower and reduces airflow, which causes its own problems. One step up, changed more often, beats a very high grade filter left in for six months.
Run an air purifier in the bedroom. One HEPA unit in the room where you spend eight hours does more for you than trying to treat the whole house. This is the single best use of one purifier.
Wash bedding weekly through the season rather than stretching it. During a long inversion, twice a week is not unreasonable if you are reacting.
Do not shake bedding out indoors. This feels productive and it is the opposite. You are putting the particulate back into the room you are standing in, and most of it settles right back down. Take it straight to the machine.
Vacuum the mattress once a season with an upholstery attachment. The mattress is the only item you cannot launder, and what settles into it stays there.
Keep windows shut during an inversion, and open them wide the day a storm clears it out. That first clean day is when you air the house.
The comforter is the untreated item
Sheets get washed weekly, so what lands on them turns over. Comforters get washed twice a year, which means a comforter can carry an entire inversion season, and it sits directly under your face when you pull it up.
Once during the winter and once at the end of it is the reasonable rhythm, on top of whatever you already do.
The reason people skip it is that a home washer cannot do it. Packed into a small drum, the comforter presses flat against the wall, water cannot move through the fill, and the particulate you were trying to remove stays in the middle along with the detergent.
The machines at our self-service laundry on 7200 South have the drum size for a full comforter to tumble freely, which is what lets water get through the fill, and a much higher extraction speed, which is what lets it dry through rather than coming out damp in the seams.
Our wash-dry-fold service covers bedding if you would rather hand it over.
Washing for particulate specifically
Wash warm rather than cold, and run an extra rinse. Fine particulate needs water volume to carry it away, and a short cold cycle mostly moves it around.
Use less detergent than the cap suggests. Residue left in fabric holds onto particles, so overdosing works against you.
Skip fabric softener. It leaves a coating that both traps particulate and increases static, and static in a dry Utah winter is already pulling dust toward your bedding.
Wool dryer balls handle the static without the coating.
The short version
Inversion particulate gets indoors regardless of how tight your house feels, and your furnace circulates it. Check the furnace filter monthly through the winter and upgrade it one step. Put a HEPA purifier in the bedroom. Wash bedding weekly, more during a long inversion, warm with an extra rinse and no softener. Never shake bedding out indoors. Wash the comforter twice over the season on a machine large enough to actually rinse it, and open the windows the day a storm finally clears the valley.
WaveMAX Midvale is at 48 West 7200 South, easy to reach from Midvale, Murray, and the surrounding valley. If you are not sure what a comforter or a specialty pillow can take, call us at (385) 557-4665 before you wash it.