The General Tersus 2000 Air Cleaner is a combination media style air cleaner and photocatalytic air cleaner. The ultraviolet lamps are wired to operate continuously. This feature allows the catalyst to burn off surface impurities, cleaning and reactivating itself during periods of non-use or no airflow. The cost of operation is less than .07 cents per day. The GeneralAire TERSus air purification system combines three unique technologies to protect people against indoor air pollutants. Photocatalytic technology (PCO) combined with high efficiency electrostatic MERV13 particulate filtration and germicidal ultraviolet light quickly reduces and eliminated toxic gas-phase chemicals, lung damaging dust and airborne germs from the living environment. Many new homes have smart programmable thermostats that allow for automatic operation of the air-handler fan unit when there is no demand for heating or air conditioning. It is important that the GeneralAire TERSus air purification system is operating at least 30 minutes per hour (24) hours per day to remove toxic materials from the indoor environment. The length of operation depends on the location of the home or office in relation to point source pollution such as refineries, processing plants, automobile traffic and areas that produce high levels of pollen. Individuals that are sensitive to mold spores, dust mites, chemicals or have respiratory problems such as asthma, emphysema, and chronic allergies should extend the run time to (40) minutes or more per hour. Air filters in this model must be replaced every 6 months. UV lamps must be replaced every 12 months.