The present invention provides an apparatus for circulating a carrier gas containing a chemical deactivating vapor or gas in a chamber. The apparatus includes a housing defining a flow path therethrough. The housing has an inlet end and an outlet end. A blower is provided for conveying a carrier gas containing a chemical deactivating vapor or gas along the flow path. A filter that includes a filter element is provided. The filter is movable between a first position and a second position, wherein the filter element is fluidly isolated from the flow path when the filter is in the first position, and the filter element is disposed in the flow path when the filter is in the second position. An actuator is provided for moving the filter between the first position and the second position.
