HIGHLY EFFICIENT UV C SOURCE

An excimer bulb assembly including a krypton/chlorine excimer bulb and a pass filter. The excimer bulb assembly does not emit substantial UV C radiation in wavelengths longer than deadly 240 nm through UV C wavelengths. The pass filter is adapted to block substantial UV C radiation in wavelengths in the range of 240 nm-280 nm. The assembly may include a captured reflector, a smart chip, and/or a heat sink. The bulb and its electrical connectors may form a cartridge. The assembly may include a housing and the cartridge may swivel in the housing.