Surround Air Intelli-Pro Spare HEPA Filter for XJ-3800 Series Air Purifier Spare filter cartridge for the Surround Air Intelli-Pro XJ-3800 air purifier. 2-in-1 combo-filter with True HEPA and Activated Carbon; Genuine Surround Air spare filter. Only Genuine Surround Air parts meet specifications necessary for optimal performance. Ultra-fibrous, ultra-absorbent True HEPA filtration is the most effective type at capturing dust and allergens. More than 99% effective. High-quality, charcoal-filled Carbon Filter is the most effective type for removing chemicals and odors. Dimensions (in): 13 x 11 x 1.25. Black rubber-foam gasket around the outside edge ensures a snug fit inside the Intelli-Pro XJ-3800 air purifier.