The filtration system was a system aboard Constitution-class starships.

In 2267, a crewman noted that the USS Constellation's filtration systems were down, following an attack by the planet killer. (TOS: "The Doomsday Machine")

In 2370, Data compared placental barrier, maternal antibodies, and amniotic fluids to a filtration system, in that they prevented viruses like the intron virus from being passed on to developing fetuses. (TNG: "Genesis")

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