The air exits the inertial separator and enters the CBRN Filter, which in most cases is of the “Composite” type. The term Composite is used to indicate the fact that this type of filter includes more than one filtration stage, in the case of the filters discussed in this document there are two filtration stages – the first being a High Efficiency Particulate Air (HEPA) filter element, used to remove any remaining fine particles from the incoming air, including the Biological threat, and the second being a bed of activated and treated carbon which removes the chemical agents.