Pre-filters (Stage one filtration): These can be disposed of as general waste as long as they are contained appropriately (in a sealed bag). This prevents any particulate from reaching breathing zones of anyone during transportation or disposal of the filter.
Combined-filters (Stage two HEPA/carbon filtration): Saturated carbon element filters are classified as hazardous waste and should be disposed of according to local disposal rules and regulations. This normally requires a special service collection and a filter history or MSDS (Material Safety Data Sheet) for the product that has been introduced to the filter. Contact your materials supplier directly to obtain an MSDS.
—John Podwojski, BOFA Americas