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In chemistry and common usage, a filter is a device (usually a membrane or layer) that is designed to block certain objects or substances while letting others through. Filters are often used to remove harmful substances from air or water, for example to remove air pollution, to make water drinkable, to prepare coffee. In domestic food and drink preparation where bulk solids are removed from liquids, this is often called a strainer.
For certain situations, such as separating an aqueous substance from a solid one, filtering may be replaced with decanting.
Filters for various substances:
Filters for specific applications:
Filters by various methods:
Related devices and concepts:
- Activated carbon
- Non-Filter (trade name).
- Gas mask
- Reverse osmosis
- Filter feeder
- Filter binding assay