A germicidal UV-C lamp is mounted inside the air handler, positioned to illuminate the evaporator coil and the air stream passing over it. Ultraviolet light at that wavelength disrupts the DNA of mould spores and bacteria, so growth cannot establish on the coil surface where condensation keeps things permanently damp. Unlike a filter, it works continuously and never loads up.
The evaporator coil is where growth actually starts, because it is wet whenever the system runs. That is where we aim the lamp.
The lamp treats air on every cycle rather than at a service interval. Bulbs are replaced annually to hold output at effective levels.
UV works best as prevention in the humid Upstate South Carolina climate, where coils stay damp for much of the year and mould returns quickly after cleaning. It suits homes with recurring microbial growth, properties with high indoor humidity, and households where someone is sensitive to mould. It supplements duct cleaning rather than replacing it, and we always clean the system first so the lamp is treating a clean coil.
Greenville summers keep evaporator coils wet for months. UV holds back regrowth between cleanings instead of letting it re-establish.
Output drops well before the lamp stops glowing. We schedule a yearly bulb replacement so the system keeps working as intended.
