Dust

For other uses, see Dust (disambiguation).

A dust storm blankets Texas homes, in 1935.

Dust is a general name for minute solid particles with diameters less than 20 thou (500 micrometres). Particles in the atmosphere arise from various sources such as soil dust lifted up by wind, volcanic eruptions, and pollution. Dust in homes, offices, and other human environments contains human skin cells, small amounts of plant pollen, human and animal hairs, textile fibers, paper fibres, minerals from outdoor soil, and many other materials which may be found in the local environment.

Domestic dust

Composition and types

Most common particles of dust are often better perceived on dark surfaces.

The precise composition of domestic dust may 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. The composition of dust also depends upon the ventilation, and heating systems, cleaning habits, activities of the occupants or users of a room, etc. House dust consists of inorganic and organic matter, and the relative proportions of these components may vary considerably. Kindergartens dust often consists almost entirely of inorganic materials like sand, loam, and clay from sand pits. On the other hand, house dust from the homes of animal owners with worn out carpets consists nearly completely of organic material. In a study of 318 house samples, the proportion of organic matter ranged from 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, ranged from 25.7% to 56.5%. Floor dust from seven Danish offices had a mean organic fraction of 33% (Mølhave et al., 2000).

Domestic dust seen under a microscope.

According to the German Environmental Survey, approximately 6 mg/(m²·d) of house dust is formed in private households, depending primarily on the amount of time spent at home. Nearly 1000 dust particles per square centimetre settle on domestic surfaces every hour. Some dust consists of human skin. Scientists estimate that humans shed the entire outer layer of skin every day or two, at a rate of 7 million skin flakes per minute, which corresponds to a mass emission rate of about 20 milligrams per minute. "Dust bunnies" are small clumps of fluff that form when sufficient dust accumulates.

Dust particles acquire a negative charge when introduced into a low pressure RF argon plasma and levitate in the sheath of the lower RF driven electrode due to a balance between the upward electrostatic force and the downward forces of ion drag and gravity. An external negative DC voltage greater than the negative self-bias is applied to the driven electrode, which further repels the plasma electrons so increasing the sheath size and moving the equilibrium height of the dust particles upwards. Increasing the negative DC voltage is found to cause the lowest dust particles to fall through the sheath to the driven electrode. The trajectories of these falling particles have been recorded with a high speed camera and analysed. The charge on the dust particles is deduced from the equation of motion. It is found that the dust particles always remain negatively charged even deep in the sheath.

Domestic dust and humans

Three years of use without cleaning has caused this laptop heat sink to become clogged with dust, rendering the computer unusable due to possibility of overheating.

Insects and other small fauna found in houses subtly interact with dust and may have adverse impact on the health of humans.

Dust may worsen hay fever. Circulating outdoor air through a house by keeping doors and windows open, or at least slightly ajar, may reduce the risk of hay fever-causing dust. In colder climates, occupants seal even the smallest air gaps, and eliminate outside fresh air circulating inside the house. So it is essential to manage dust and airflow..

House dust mites exist on all indoor surfaces and even suspended in the air. They feed on minute particles of organic matter, the main constituent of house dust. Dust mites flourish in the fibers of bedding, furniture, and carpets. They excrete enzymes to digest the organic particles, and excrete feces, that together become part of the house dust, and may irritate allergies.

Alternately, the hygiene hypothesis posits that the modern obsession with cleanliness is as much a problem as house dust mites. The hygiene hypothesis argues that our lack of prior pathogenic exposure may in fact encourage the development of ailments including hay fever and asthma.

Atmospheric dust

Large dust storm over Libya.

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 minute particles are dispersed within the air in a given area (such as flour or coal dust), under certain circumstances can cause an explosion hazard.

Coal dust is responsible for the lung disease known as Pneumoconiosis, including black lung disease, that occurs among coal miners. The danger of coal dust resulted in environmental legislation regulating work place air quality in some jurisdictions.

Road dust

Dust kicked up by vehicles traveling on roads, may make up 33% of air pollution Road dust consists of deposition of vehicle exhausts and industrial exhausts, tire and brake wears, dust from paved roads or potholes, and dust from construction sites. Road dust represents a significant source contributing to the generation and release of particulate matter into the atmosphere. Control of road dust is a significant challenge in urban areas, and also in other spheres with high levels of vehicular traffic upon unsealed roads such as mines and garbage dumps. Road dust may be suppressed by mechanical methods like sweeping vehicles, with vegetable oils, or with water sprayers.

See also: road debris

Dust control

Control of atmospheric dust

The U. S. Environmental Protection Agency (EPA) mandates facilities that generate dust minimize or mitigate the production of dust in their operation. The most frequent dust control violations occur at new residential housing developments in urban areas. United States Federal law requires that construction sites obtain permits to conduct earth moving, and include plans to control dust emissions. Control measures include such simple practices as spraying construction and demolition sites with water, and preventing the tracking of dust onto adjacent roads. US federal laws require dust control on sources such as vacant lots, unpaved parking lots, and unpaved roads. Dust in such places may be suppressed by mechanical methods , including paving or laying down gravel, or stabilizing the surface with water, vegetable oils or other dust suppressants, or by using water misters to suppress dust that is already airborne .

Control of domestic dust

Dust control is the suppression of solid particles with diameters less than 500 micrometers. Dust in the airstream poses a serious health threat to children, older people, and those with respiratory illnesses. House dust can become airborne easily. Care should be exercised when removing dust to avoid causing the dust to become airborne. Some dust removing devices trap some dust. One way to repel dust is with an electrical charge . Water-trap vacuums such as the Rainbow, eliminate the risk of broadcasting dust by drowning the dust particles in water. Dust subsequently cannot escape the container to fly back into the air.

Control of dust resistance on surfaces

A dust resistant surface is a state of prevention against dust contamination or damage, by a design or treatment of materials and items in manufacturing or through a repair process. A reduced tacticity of a synthetic layer or covering can protect surfaces and release small molecules that could have remained attached. A panel, container or enclosure with seams may feature types of strengthened rigidity or sealant to vulnerable edges and joins.

Dust in other contexts

• Dust Accelerates Snowmelt in the San Juan Mountains
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  2005 (Less dust)
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  2006 (More dust)
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  2008 (Less dust)
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  2009 (More dust)

Dust in outer space

Cosmic dust is widely present in space, where gas and dust clouds are primary precursors for planetary systems. The zodiacal light seen in the dark night sky, is produced by sunlight reflected from particles of dust in orbit around the Sun. The tails of comets are produced by emissions of dust and ionized gas from the body of the comet. Dust also covers solid planetary bodies, and vast dust storms occur on Mars that cover almost the entire planet. Interstellar dust is found between the stars, and high concentrations produce diffuse nebulae and reflection nebulae.

Dust is widely present in the galaxy. Ambient radiation heats dust and re-emits radiation into the microwave band, which may distort the cosmic microwave background power spectrum. Dust in this regime has a complicated emission spectrum, and includes both thermal dust emission and spinning dust emission.

Dust samples returned from outer space may provide information about conditions in the early solar system. Several spacecraft have sought to gather samples of dust and other materials. Among these craft was Stardust, which flew past Comet Wild 2 in 2004, and returned a capsule of the comet's remains to Earth in January 2006. The Japanese Hayabusa spacecraft is on a mission to collect samples of dust from the surface of an asteroid.

Art and entertainment

Stippling and airbrushing are fine art techniques that can create dust. In video games, a particle system is usually used.

Gallery

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  Dry, windy weather sends clouds of dust across south-eastern Australia.
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  A pale brown plume of dust sweeps out of Argentina’s Pampas.
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  A thick dust plume over Kuwait and the north-western tip of the Persian Gulf.

See also

• Contamination control
• Dust explosion
• Medical geology
• Mineral dust
• Sawdust

References

• Holmes, Hannah; (2001)The Secret Life of Dust. Wiley. ISBN 0-471-37743-0
• Steedman, Carolyn; (2002) Dust. Manchester University Press. ISBN 978-0719060151

External links

• The Bibliography of Aeolian Research
• The German Asthma & Allergy Federation (DAAB) Template:De icon