Patent ID: 7510470

Claim:
An air processing system comprising: a first inlet to receive air from a continuous space; a second inlet to receive air external to the space; a first outlet portion and a second outlet portion including first and second outlets, respectively, to and in communication with the space; a first filtration portion for filtering air received from the first and second inlets and supplying the filtered air to the first outlet portion; an isolated housing coupled to the first and second outlet portions and defining a flow path extending from the first outlet portion to the second outlet portion; a second air filtration portion disposed in the flow path of the housing and downstream of the first outlet portion, wherein the second filtration portion is adapted to be capable of selectively filtering at least a first agent from air and the first filtration portion is adapted to not be capable of filtering the first agent from air; wherein the second outlet portion is downstream of the second air filtration portion, wherein, during operation of the system for filtering the received air, the first and second outlets always are in communication with the first inlet; and a valve to selectively direct air between the first outlet and the second air filtration portion; wherein, in a first position of the valve, the filtered air received at the first outlet portion from the first filtration portion is supplied to the space only through the first outlet, and wherein, in a second position of the valve, the filtered air received at the first outlet portion from the first filtration portion is filtered by the second filtration portion and then supplied to the space only through the second outlet.