Air ventilation and filtration apparatus

Apparatus for exchanging air within an enclosure with outside air while subjecting air within said enclosure to gas filtration comprising'

• a housing;
• ducting extending within said housing to provide a central chamber having four ports, each port being in communication with a port in said housing to establish four air flow channels;
• exhaust fan means mounted in a first of said channels to produce air flow from said enclosure;
• air supply fan means mounted in a second of said channels to produce air flow into said enclosure;
• air treatment means located in a third of said channels, said third channel being ported to said enclosure and said air treatment means being selected from the group consisting of gas filtration means and electronic air cleaning means;
• a heating storage matrix located in a fourth of said channels, said fourth channel being ported to outside air;
• and
• valve means disposed in said central chamber and being positionable with respect to said four ports within said chamber to establish a first operating mode in which said first channel is in air flow communication with said fourth channel and said third channel is in air flow communication with said second channel, and a second operating mode in which said first channel is in air flow communication with said third channel and said fourth channel is in air flow communication with said second channel.