Page "Fume hood" Paragraph 25

After pre-filtration, the fumes are sucked through a layer of activated charcoal which absorbs the majority of chemicals that pass through it.

Ammonia and carbon monoxide will, however, pass through most carbon filters.

Additional specific filtration techniques can be added to combat chemicals that would otherwise be pumped back into the room.

A main filter will generally last for approximately two years, dependent on usage.