Air purifier

摘要

An air purifier in which an electrically driven fan 11 draws air though a replaceable filter 12 includes an air quality sensor 13 and a programmed microcomputer 14 to alter the speed of the fan in response to signals from the sensor. Fan speed increases when air quality, eg the average number of particles of more than 1 micron per unit volume, is poor or deteriorates. The fan may be automatically turned off when air quality is above a certain value. The cabinet 10 housing the fan and filter may also include a visual display 15 of air quality as detected by the sensor 13. A filter replacement indicator 16 may be lit up by the microcomputer according to a computation based on both accumulated time periods of fan operation and actual fan speeds during use.