A germicidal lamp may include a glass envelope and a UV-blocking coating provided on the glass envelope. An HVAC system may include a duct, evaporator coil banks provided in the duct, a drip pan provided in the duct and below the evaporator coil banks, and a germicidal lamp inserted through an opening in the duct and configured to emit UV radiation. The germicidal lamp may include a glass envelope and a UV-blocking coating provided on the glass envelope, and the UV-blocking coating may be configured such that the evaporator coil banks are irradiated with UV radiation while a substantial portion of the UV radiation is prevented from reaching the drip pan.
