Abstract: A method and apparatus is provided for exhausting air from the interior of the occupant compartment of a movable vehicle to protect occupants from undesirable or contaminated air originating within or outside the vehicle. The method incorporates an exhaust system to remove air from the rear of the vehicle while maintaining air flow through the vehicle, preventing air back streaming, and sustaining a relative negative air pressure inside the occupant compartment. The invention prevents the breathing of air contaminated by people or animals being transported in vehicles and can protect occupants from diseases, odors, bio-hazards, and other undesirable or contaminated air in an enclosed compartment.