UV stands for ultraviolet. The germicidal capabilities of UVC light were used for years in hospitals and other areas where bacteria count is typically high. It was found that UVC light didn't just disinfect surfaces; it could also be used to disinfect the air. Normally, air purifiers that include UVC expose the air to UVC light. Others use UVC light to shine on a photocatalyst and create ions that disinfect air. UVC light alone isn't a great standalone solution for most residential or commercial settings due to the fact the UVC light requires a long dwell time on contaminants to be effective. Air passing through an air purifier or a furnace system moves too fast for UVC light alone to effectively deactivate contaminants.