AC ventilation cleaner aerosols freshen the air ducts in a car. Unlike foaming cleaners, these sprays are misted directly into the cowl fresh air intake below the wipers. This is done with the blower fan running on high to pull the mist through the entire HVAC system.
The aerosol mist travels through the blend doors, heater core, and dashboard vents. It kills odor-causing bacteria and leaves a fresh scent behind. It is an easy way to clean vents without taking the dash apart.
Always remove the cabin air filter before spraying. If left in place, the paper filter will absorb the chemical mist. This blocks the cleaner from reaching the vents and ruins the filter.