Activated Carbon Filter upgrade boosts RA-650 functionality HEPA filtration is increasingly seen as the single most important safety device available for creating a safe environment for jobsite workers. Now, with the Activated Carbon Filter, the RA-650 can play an even more important role in keeping an enclosed environment clean and safe - both for workers and for occupants. The activated carbon filter now equips the RA-650 to capture a wide variety of volatile organic compounds (VOCs), including soot and smoke, food odors, fumes from paint and paint thinners, sewer odors and many other compounds. No modification of the RA-650 is required - users simply place the new carbon filter inside the cabinet in front of HEPA filter and then re-secure the cover. Capacity of the carbon filter will vary widely depending on conditions, but it should be replaced when a decline of effectiveness is noted.