Most of your air is indoors
Open the blinds on a sunny morning and watch the light hit the air. All of that was there in the dark too, and you were breathing it.
The US Environmental Protection Agency puts the exposure in a sentence: Americans spend about 90% of their time indoors (EPA, Report on the Environment). Indoors, the same page says, some pollutants often run 2 to 5 times higher than typical outdoor levels. The people most sensitive to pollution, the very young, older adults and anyone with heart or lung disease, tend to spend even more of their day inside.
The EPA page also lists what can set off an asthma attack in someone who is susceptible: dust mites, mold, pet dander, tobacco smoke, cockroach allergens and particulate matter. The numbers behind that list aren’t small. In 2023, asthma affected 27.8 million people in the US (CDC, most recent national asthma data). That’s 8.4% of the population. Among them were 4.8 million children.
Cleaning isn’t medicine, and nothing here replaces a doctor’s plan. But several of the triggers on that list live in dust and fabric, and dust and fabric are what cleaning is for.
Meet the dust mite
You can’t see one. That’s the whole problem with them.
About 20 million people in the US are allergic to dust mites, according to the Asthma and Allergy Foundation of America. The mites eat the skin flakes you shed every day, and the flakes work deep into bedding, mattresses, carpet, upholstered furniture and soft toys. They like it warm, around 70°F and up. They like it humid, above 50%.
The foundation’s advice is specific, which is the nice thing about it. Wash sheets, blankets and throw rugs every week in water of at least 130°F, and dry them on a hot cycle. Zip allergen-barrier covers onto mattresses and pillows; the pores are too small for mites and their waste to pass through. Keep indoor humidity between 30% and 50%. Vacuum weekly with a HEPA filter, so what you pick up doesn’t go straight back into the air.
The CDC’s asthma guidance says the same things in a different order: allergen-proof mattress and pillow covers, bedding washed weekly and dried completely, regular vacuuming with a HEPA vacuum, and relative humidity held around 30% to 50% (CDC, controlling asthma triggers).
The dog, the damp, the rest
The dog is on the bed again. The CDC has an opinion about that.
Its page on asthma triggers takes the household offenders one at a time. Furry pets can set off an attack in people who are allergic to them, and the first step is to keep them out of bedrooms, with covers and a HEPA air cleaner as backup. Breathing in mold can trigger an attack whether or not you’re allergic to it, so keep humidity under 50%. Dry anything wet within 24 to 48 hours. Cockroaches and other pests answer to the boring fixes, food and water put away and cracks sealed, and the CDC warns against sprays and foggers, which can set off an attack on their own.
The allergy foundation adds the habits that make all of this easier: keep surfaces clean and uncluttered, dust with a damp cloth rather than a dry one, and shut the bedroom door when you leave the house so the dog stays off the bed (AAFA, controlling indoor allergens).
What the spray puts back
Cleaning can add to the air as well as take from it. Anyone who has coughed in a freshly bleached bathroom knows this already.
The EPA reports that many volatile organic compounds run consistently higher indoors than out, up to 10 times higher, and it names cleansers, disinfectants, air fresheners and paints among the sources (EPA, volatile organic compounds). Its advice is short. Open windows when you use such products. Meet the label’s precautions, or go further. Buy only what you’ll use. Never mix household products unless the label says to.
If you have asthma or a sensitivity, keep the list of products short and read the label before the product comes home. Air fresheners are on the EPA’s list of sources, so leave them out; an open window after cleaning clears the air without adding anything to it. Whoever does the cleaning in your home should know which products to skip.
The air routine, on one table
Pulling the agencies’ advice into one place:
| How often | What | Why |
|---|---|---|
| Every week | Bedding washed at 130°F or hotter, dried hot | Kills dust mites where they are densest |
| Every week | Floors, rugs and upholstery vacuumed with a HEPA filter | Removes mites, dander and dust without recirculating them |
| Every week | Surfaces dusted with a damp cloth | A dry cloth moves dust; a damp one lifts it |
| When wet | Towels, mats and spills dried within 24 to 48 hours | Mold needs moisture and time |
| Each season | Vents, vent covers, baseboards and door frames wiped | Where settled dust collects and is stirred up by heating and cooling |
| Always | Humidity 30% to 50%, windows open when using strong products | Starves mites and mold; clears VOCs |
The seasonal row is the easiest one to skip, because nothing there looks dirty from across the room. Baseboards, door frames, vents and vent covers collect dust slowly, and the first run of the furnace stirs it all up, so wipe them in every room 4 times a year, with one of those passes just before the heating season. Denver’s dry air changes the shape of some of this list; Denver’s dry air and dust covers that. For tonight, one thing: strip the bed and start the hot wash. The mites won’t see it coming.