Filter

[edit] What does filter mean?

The word 'filter' is both a verb, meaning the act of passing through something or moving slowing in a certain direction and a noun, referring to a system by which an object moves in a certain direction or the object through which something passes. A filter is usually an object that can separate certain elements from one another, often removing unwanted parts or impurities such as particles from materials, liquids or gas that pass through, this can also be used in electronics as well as digital systems.

In the design and construction of buildings and cities there are two common uses of the term, the first relatively simple application and the second with a wider set of applications.

In city, urban or traffic planning and management a filter may be used to refer to a system of traffic management, where by vehicles filter left or right within a road junction or traffic light or signage system. The term can also be used in the design of pedestrian traffic systems in buildings or the urban realm, also referred to more generally as people-movement (as in crowd flow, way-finding and evacuation) where route-ways, layout, signage or indicators act as filters to encourage pedestrians in one direction or another. This theme touches on a number of design and research areas such as crowd flow, way-finding, evacuation, place-making, and urban simulation.

In terms of building design and construction, filters are often key component parts of building service systems; in air systems, they filter particles, in water systems, they remove minerals, and in gas systems, they remove solid particles from the flow. Filters are also used in electronic systems to remove unwanted frequencies from electric or other signals.

Filters are also common place component parts of domestic appliances such as washing machines, dishwashers, tumble driers, steamers, fryers etc. Filters in each of these systems vary in their design, task, function, longevity, and maintenance requirements, and there are likely to be classification systems to describe their type and the substances they can actively separate, as well as their class, which describes the grade of material they can filter and their capacity to remove and effectively absorb unwanted elements.

[edit] Types of filters

[edit] Air filters

• HEPA filters.
• Washable filters.
• Electrostatic filters.
• UV light filters.
• Media filters.
• Spun glass filters.
• Pleated filters.

[edit] Water filters

• Mechanical Filters.
• Absorption Filters.
• Sequestration Filters.
• Ion Exchange Filters.
• Reverse Osmosis Filters.

[edit] Gas filters

• Types
• Class 1-3

[edit] Electronic filters

• Passive filters
• Active filters
• Analog filters
• Digital filters
• High-pass
• Low-pass
• Band-pass
• Band-stop (band-rejection; notch)
• All-pass.
• Discrete-time (sampled)
• Continuous-time
• Linear
• Non-linear
• Infinite impulse response (IIR type)
• Finite impulse response (FIR type)

[edit] Related articles on Designing Buildings

• Clean indoor air for healthy living - New air filter standards
• Filter
• Filter strip
• Hepa filter
• Options framework filter
• Roll filter
• Types of air filter

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