Germicidal Lamps emit a blue glow to indicate the lamp is on. The blue glow is not the Ultraviolet rays but visible light for the operator to know power is running through the lamp. This blue glow will last long past the ability of the lamp to emit the necessary 253.7 nanometers of germicidal effectiveness. To maintain the highest degree of efficiency in your sterilizer, the lamp should be replaced between 9 months and 1 year. Eight thousand hours is the maximum effectiveness of most germicidal lamps. The UV breaks down the quartz containment glass and reduces effectiveness. Eventually it prevents the UV from emitting from the lamp.