It is recommended that you leave the germguardian UV-C Room Air Sanitizer running continuously.

The germguardian® UV-C Room Air Sanitizer uses a replaceable 9-watt UV-C bulb to eliminate over 99% of targeted airborne germs, and a filter to destroy odors and allergens like dust mites and mold spores.

The 9-watt UV-C bulb and filter fits into all EV9102 models and should be replaced every 6-8 months depending on use.
Both the UV-C bulb and filter are sold together as a single replacement pack.