AS-IH-1003 17" T3 Quartz Enclosed Bulb. Residential UVC lamps should be replaced every 9000 hours or approximately every 12 months. If your lamp is strictly used for keeping coils clean on your HVAC unit, you can save money and the environment when you use your lamps for their maximum two-year life span. For people with respiratory conditions or other acute sensitivities, we strongly recommend keeping to an annual lamp replacement schedule.