Abstract: The air purifiers in the present invention can be mounted in a ceiling, positioned on a floor, or completely self-contained. The air purifiers sterilize the air using high-output UV-C energy and a unique multi-chambered internal design to kill viruses, bacteria and allergens is disclosed. The invention is designed to kill airborne pathogens, require no maintenance for 10,000 hours or more, use the highest dosage of 253. nm UV-C light energy of any ceiling-mounted unit, produce the longest exposure time of any ceiling-mounted air sterilizer (>1.0 sec.), use two quite (15 db) fans to control the airflow through the multi-chambered kill zone, operate quietly while positioned in the ceiling or on the floor, and designed to be inexpensive to manufacture.