Composition and types

The precise composition of domestic dust can vary widely:

The quantity and composition of house dust varies greatly with seasonal and environmental factors such as the surroundings, exchange of outside air, age of the house, building materials and their condition, and the quantity of furniture and carpets, as well as their state of preservation. It varies further with ventilation and heating systems, cleaning habits, activities of the occupants or users of a room, etc. House dust consists of inorganic and organic matter, yet the relative proportions of these components may vary considerably. "House dust" from kindergartens often consists almost completely of inorganic materials such as sand, loam, and clay from sand pits. On the other hand, house dust from residences of animal owners with worn out carpets may consist nearly completely of organic material. The proportion of organic matter in 318 house dust samples was found to vary between <5% and >95% (Butte and Walker, 1994). Fergusson et al. (1986) reported the organic content of house dust from 11 homes in Christchurch, New Zealand, to be within the range from 25.7% to 56.5%. Floor dust from seven Danish offices had a mean organic fraction of 33% (Mølhave et al., 2000).

According to the German Environmental Survey, approximately 6 mg/m²/day of house dust is formed in private households, depending primarily on the amount of time spent at home. Nearly 1000 dust particles per square centimeter settle on domestic surfaces every hour.Kathleen Hess-Kosa, (2002), Indoor Air Quality: sampling methodologies, page 216. CRC Press. Some dust consists of human skin; it is estimated that the entire outer layer of skin is shed every day or two at a rate of 7 million skin flakes per minute, which corresponds to a mass emission rate of about 20 mg/minute. "Dust bunnies" are little clumps of fluff that form when sufficient dust accumulates.

Domestic dust and humans

Insects and other small fauna found in houses have their own subtle interactions with dust that may have adverse impact on the health of its regular occupantsFact: date=October 2008. Dust may worsen hay fever. Thus, in many climates it is wise to keep a modicum of airflow going through a house, by keeping doors and windows open or at least slightly ajar. In colder climates, it is essential to manage dust and airflow, since the climate encourages occupants to seal even the smallest air gaps, and thus eliminate any possibility of fresh air enteringFact: date=October 2008.

House dust mites are on all surfaces and even suspended in air. Dust mites feed on minute particles of organic matter, the main constituent of house dust. They excrete enzymes to digest dust particles; these enzymes and their feces, in turn, become part of house dust and can provoke allergic reactions in humans. Dust mites flourish in the fibres of bedding, furniture, and carpets.