Review on Cozmor Air Purifier: Large Room H13 True HEPA Filter with Smart Auto Sensor - Eliminate 99.98% Odors, Mold, Pollen and Smoke, Perfect for Bedroom and Office. Includes Sleep Mode, Timer, and Child-Lock by Rachael Taylor

This filter has a changing color air quality display as well as a numeric ppm2 display, in contrast to the lack of an air quality monitor on my first more expensive small bedroom HEPA filter. The fan runs very slowly when the air is clean and gradually increases the fan speed when the air becomes less clean, reducing indoor air pollution to safe levels faster. The timer lets you turn it off a pre-determined time so I don't leave it on all night when not needed. I use about 400 square meters including the corner of my home office. This filter keeps my indoor air in a safe range while Northern California's summertime outdoor air is now often moderately or very hazardous due to heavy fire smoke.