Honeywell Enviracaire Air Purifier Model no 51500 Honeywell Enviracaire Air Purifier Model no 51500 HONEYWELL AIR PURIFIER MODEL- 51500 FEATURES Enviracaire Air Purifier For Medium Rooms (15 ft x 15 ft) True HEPA Filter is 99.97% effective at reducing airborne particles from the air passing through it, such as pollen, cat dander, household dust, mold spores and tobacco smoke. Intelli-check feature monitors HEPA and Pre-filter usage. Activated Carbon Pre-filter helps reduce odors and extends HEPA filter life. Multiple Air Cleaning power levels. Patented 360 degree Air Intake and Discharge for effective air cleaning power. Top Air Discharge Neutral white color for background blending. Replacement Prefilter is 38002 Replacement HEPA type filter is 21500 Included FREE HONEYWELL UNIVERSAL PRE-FILTER *Fits all round Honeywell models *Reduces odors, captures large particles, extends HEPA filter life