Quote:
Originally Posted by YellowPages
(Post 14140410)
What is dust?
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http://www.funsci.com/fun3_en/dust/dust.htm
http://en.wikipedia.org/wiki/Dust
Dust is a general name for minute solid particles with diameters less than 500 micrometers. On Earth, dust occurs in the atmosphere from various sources; soil dust lifted up by wind, volcanic eruptions, and pollution are some examples. Airborne dust is considered an aerosol and can have a strong local radiative forcing on the atmosphere and significant effects on climate. In addition, if enough of the minute particles are dispersed within the air in a given area (such as flour or coal dust), under certain circumstances this can be an explosion hazard.
Coal dust is responsible for the lung disease known as Pneumoconiosis, including black lung disease, which occurs among coal miners. This danger has resulted in a number of laws regulating environmental standards for working conditions.
Dust in homes, offices, and other human environments consists of human skin cells, plant pollen, human and animal hairs, textile fibers, paper fibers, minerals from outdoor soil and dust, and many other materials which may be found in the local environment.[1] 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).[2]
According to the German Environmental Survey, approximately 6 mg/m²/day of house dust is formed in private households,[3] depending primarily on the amount of time spent at home. Nearly 1000 dust particles per square centimeter settle on domestic surfaces every hour.[1] 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.[4]
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 occupants. 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 entering.
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 fibers of bedding, furniture, and carpets.
The particles that make up house dust can easily become airborne, so care must be exercised when removing dust, as the activity intended to sanitize or remove dust may make it airborne. One way to repel dust is with some kind of electrical charge, but house dust can be removed by many methods, including wiping, swiping, or sweeping by hand, or with a dust cloth, sponge, feather duster, or broom, or by suction by a vacuum cleaner or air filter. The device being used traps the dust; however, some may become airborne and come to settle in the cleaner's lungs, thus making the activity somewhat hazardous. "Dust bunnies" are little clumps of fluff that form when sufficient dust accumulates. Dust is known to worsen hay fever.
