An apparatus for converting a toxic gas to benign substances comprises a housing characterized with multi-stages including a first stage, a second stage, a third stage and a fourth stage coupled to one another in sequence, wherein the first stage comprises a catalytic system configured to convert the toxic gas into its derivatives; the second stage comprises a carbonaceous fibrous material adapted to capture the remaining toxic gas and the derivatives; the third stage comprises at least one oxidizer to oxidize the remaining toxic gas to benign substances including CO2 and water; and the fourth stage comprises a scrubber configured to remove all of volatile organic compounds or water molecules generated as part of the first and third stages.