The purifier runs on high to clean the air faster if it’s bad. The fan runs on low to conserve energy if the air is fine. Though it’s Energy Star-certified, the Honeywell HPA300 True HEPA Air Purifier doesn’t have an Auto mode and had high power consumption in our tests. We have always judged purifiers… Continue reading Honeywell HEPA Large Room Air Purifier, Black HPA200