Air purifier-combination filter

A pollution cleaning system for the passenger compartment of a motor vehicle, comprising:

• a plenum;
• a filter positioned in the plenum and including a housing containing a replaceable filter element having multiple layers providing a surface area for contact with air passing therethrough, to remove pollutants emitted from exhaust fumes and allergens-pollen from the air, and prevent such pollutants from entering the motor vehicle interior,
• an air inlet for introducing outside air into said plenum;
• a heater located between the air inlet and the filter to raise the temperature of the outside air by an amount necessary to protect the filter from freezing and to keep the filter dry and monitoring means for generating an electrical signal indicating that said filter is clogged with dirt, said monitoring means including a sensor switch having a movable sensor plate mounted on the downstream side of and in the path of air flowing through said filter so as to be moved to a first position in which said switch is open and said signals prevented from being generated, said monitoring means including means of biasing said sensor plate to a second position in the absence of sufficient air flow through said sensor switch generating said signal in response to the movement of said sensor plate to said second position.