ClenAir HVAC Odor Block is not a perfume mask or cover-up. The unique ClenAir formula molecularly reacts with the airborne odor-causing compounds and eliminates them and other indoor pollutants leaving clean, fresh, air behind. The HVAC Odor Block makes it easy to remove odors and improve the indoor air quality in the entire home or building by treating the air through the HVAC system. Eliminates odors caused by mold, mildew, bacteria, pets, smoke, musty odors, water damage, fire damage, paints, chemicals, animal decay, stale air, garbage areas, sewer gases, skunks, and more! Use in A/C units, furnaces, rooftop units, fan coil units, and air handlers. Residential HVAC Odor Block treats up to 3 ton systems for 2 months. Commercial HVAC Odor-Block treats 10 to 15 ton systems for 4 months.