Biofilter

A scanning device built into Star Fleet transporters that scans the incoming matter stream for, and filters out, many kinds of known hazardous bacteria and viruses.

It is not effective against organisms for which it has not been programmed. It also cannot filter organisms that exist as both matter and energy, because it cannot tell it apart from the matter stream. The transporter operator will be warned if the transporter has detected these hazards, and if they can or cannot be removed from what is being transported. A biofilter could be reprogrammed to filter out specific molecular patterns. Everything that passes through the biofilter is kept in a separate section of the transporter logs.

Biofilters are also present in certain replicators, as well as holodecks. The holodeck biofilter is a filtration device incorporated into Federation holodecks that collected organic material left by the users. This allowed for the holodecks to stay clean, and users to not worry about the effects their holographic environment may have on the ship (i.e., food waste, animal waste, hypothetical experiment waste).