I hoped this would help with the construction dust following Hurricane Harvey. It always seems to be on red, so I purchased 3 more units for nearby rooms. It still remains red all the time. I worry because both my grandaughter and I have asthma, and our air quality always seems to be bad according to the machine. I am hoping it is just the post construction debris flowing through because I have been pleased in the past with their machines. It also did an excellent job in the apartment when we were displaced.