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Filters
A filter, in general, is a component of a larger device that
removes something unwanted from a substance. There are many
types of filters, even text filters for websites and chat
rooms. Exactly what is being filtered determines exactly how a
filter works. Here are some of the most common types of
filters.
Air Filters
An air filter is designed to remove particulate matter from
the air. Many different types of filters have been invented
and are still used, each with different properties.
The most popular are the HEPA filters (High Efficency
Particulate Air). These filters are made of sheets of randomly
arranged fibers that are stacked together. The effect is like
layering fishing nets, one of top of the other, so that
particles that pass through one sheet will eventually be
caught by another.
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Electronic filters are also popular since they can be
inexpensive and efficient. These filters use electric charges
to attract dirty air particles so they stick to strips of
metal aligned in front of a fan. Air filters that look like
tall, thin columns are often electronic filters.
There are also gas filters and hybrid filters, however these
are mostly used for industrial purposes and have many
drawbacks that make them inconvenient for home use.
Water Filters
Water filters are similar in function to air filters although
the mechanisms are different because of the properties of
water.
Carbon water filters are the most used method in homes and
businesses. These are usually small devices that contain a
type of carbon made from coconuts. The carbon draws impurities
out of the water, allowing only the pure liquid to pass
through.
Reverse osmosis filters are sometimes attached to the water
systems in homes or to water coolers. This system uses high
pressure and a very, very fine sieve to purify the water. The
process can be slow, and it is power intensive, so this is not
often used.
Distilled water filters use the natural cycles of evaporation
and condensation to purify liquid. Distilled water is allowed
to evaporate, so only the water vapour rises, where it is
caught and cooled. The resulting condensate is collected as
distilled water.
There are other more experimental types of filters for both
air and water. Ideas such as ultra-violet or atmospheric gas
filters exist but have little practical use at the moment.
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