Rediair Replacement HEPA 14 Filter Pack - 1 Pair Seconds after activation of the Rediair Air Purifier, contaminated air is drawn through 3 layers of filtration. The nylon pre-filter, composite carbon cloth and HEPA 14 filters capture particulates as small as 0.3µm and expel purified air back into the room, providing up to 5 air changes an hour within a space up to 120m3. Dual HEPA 14 filters feature a composite carbon layer. Rediair's dual HEPA 14 filters are 10x more effective than domestic HEPA 13 filters