My $50 (without the HEPA filter) air purifier can detect particles and change fan speed accordingly. It also has a light sensor to go into really quiet mode dur

My $50 (without the HEPA filter) air purifier can detect particles and change fan speed accordingly. It also has a light sensor to go into really quiet mode during the night. Though, looking it up it seems that prices for the Winix Zero (including one set of filters) have doubled since I last bought one.