Delta Power Tools 50-875T2 3 Speed Ambient Air Cleaner Dirty Filter Indicator determines efficiency of the filter and needle points to red when it is time to replace 3 Speed operation, 540, 730 and 1,200 CFM Remote control offers convience for off/on, speed adjustment and timer programming Timer setting from 1/2 ouhr to 4 hours Outer Pre-filter 5 micron, Inner filter 1 micron