You might be doing it every time you do your laundry.
Surprisingly, hanging damp clothes on indoor clothing racks can be a shocking source of indoor pollution, according to Scottish scientists from the Mackintosh Environmental Architecture Research Unit at the Glascow School of Art. After conducting a three-year study on public housing units, they concluded that drying laundry inside of your home is accompanied by dangerous health hazards.
The average home has between 1 and 2.5 gallons of water in the air at any given time, according to the study. But a load of laundry can release an additional half gallon into the air, leaving behind all kinds of unhealthy agents that you later inhale.