Filter assembly for protecting motor vehicle occupants from pollution

In an air purification system for protecting motor vehicle occupants from pollution, the system adapted for a motor vehicle having a passenger compartment and a source of hot liquid for heating, and comprising:

• a plenum in communication with the passenger compartment of the vehicle, the plenum having
• a first air inlet adapted to receive outside air from outside the passenger compartment into said plenum,
• a second air inlet adapted to receive inside air from said passenger compartment into said plenum, and
• a blower operable to move air from said plenum into said passenger compartment,
• a first filter with at least one replaceable filter element, located in the first air inlet, for removing pollutants from the outside air,
• a second filter with at least one replaceable filter element, located in the second air inlet, for removing pollutants from the inside air,
• door means located downstream of said first and second filters and downstream of said air inlets, adapted to assume a plurality of positions in said plenum in blocking relationship to air being moved through said first air inlet and/or the second air inlet to selectively admit the outside air and/or the inside air to said blower, and
• a hot liquid heater located upstream of the first filter in the path of the outside air and adapted to raise the temperature of the outside air for protecting the first filter from freezing and for keeping it dry, the heater having heat exchange means for hot liquid from said hot liquid source.