Filter
A filter was any device, mechanism, agent or procedure that could be used to separate or remove an unwanted agent or desired byproduct from a product.

Types of filters 
 Air filtering system
 Barystatic filter
 Biofilter
 Carbon dioxide filter
 Carbon filter
 Deuterium filter
 Filter band/filter bandpass
 Encoding filter
 Narrowband filter
 Theta band filter
 Wideband filter protocol
 Filter mask
 Holodeck biofilter
 Impulse response filters
 L-90 enhanced resolution filter
 Osmotic filter
 Quantum filter
 Perceptual filter
 Plasmatic filter
 Warp plasma filter

Things with filtration abilities 
 DNA
 Environmental controls/Environmental control system
 Intake manifolds
 Sensors

Things that could be filtered out 
 Communication distortions ()
 "Human factors" ()
 Sedatives ()
 Sub-harmonic distortions

See also
 Filter bracket

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