Myth or Fact: Is Household Dust Mostly Dead Skin?
It's one of the most repeated facts about cleaning, and it's mostly wrong. Here is where dust really comes from, and why the house feels dustier once the heating is on.
By Daniel HartmannHardware Reviewer
You dusted on Saturday and by Wednesday there's a grey film on the TV stand again. The explanation you've probably heard is that most household dust is dead human skin, so the more people at home, the more dust.
That matters, because it changes where you should focus if you want less dust.
What dust is actually made of
In 2009, David Layton and Paloma Beamer of the University of Arizona published a model of how house dust forms in the journal Environmental Science & Technology. It treats dust as a mixture of organic matter such as shed skin and fibres, soil tracked in on footwear, and particles from outdoor air that get into the home (Layton and Beamer).
Speaking to NPR about the research, Beamer said roughly one-third of house dust comes from indoor sources, such as carpet fibres, and about two-thirds from outdoors, through soil tracked in and particles in the air (NPR). Indoor ingredients include fibres from carpets, furniture and bedding, skin flakes, pet dander and insect debris.
The mix varies a lot from home to home. A house with a dog, carpets and a busy front door will have very different dust from a small flat with hard floors. But "mostly dead skin" doesn't match the research.
Why it feels dustier in winter
Several things change when the heating comes on. Forced-air heating moves air, and the dust in it, around the house. Windows stay shut, so particles that come in settle rather than leave. Heating also dries the air, and dry air builds static, which helps dust cling to screens and plastic. The US Environmental Protection Agency recommends keeping indoor humidity below 60%, ideally between 30% and 50% (US EPA). In many heated homes in winter it falls to the bottom of that range or below.
What actually reduces dust
- Stop it at the door. A good mat outside and inside, and shoes off indoors, cut the soil that gets tracked in.
- Dust damp, not dry. A slightly damp microfibre cloth picks dust up. A feather duster mostly moves it into the air.
- Dust first, then vacuum, ideally with a vacuum that has a HEPA filter.
- Change the furnace or HVAC filter as often as the manufacturer recommends, using the best-rated filter your system can handle.
- Wash bedding weekly. Beds collect fibres, skin and dust mites.
- Watch the humidity. If it's very low, a humidifier set to stay within the recommended range can help with static.
The bottom line
Your house isn't dusty because you're shedding. It's dusty because the outside keeps coming in, and in winter it has fewer ways out. Focus on the door, the filter and the cloth.
Sources
- Layton, D. W. and Beamer, P. I., "Migration of Contaminated Soil and Airborne Particulates to Indoor Dust", Environmental Science & Technology (2009)
- NPR, The Dirt On Dust (2009)
- US Environmental Protection Agency, A Brief Guide to Mold, Moisture and Your Home
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