Abstract: A combined air-supplying/air-purifying breathing system that includes a self-contained breathing apparatus, a facepiece for delivering breathable air from the self-contained breathing apparatus to a user, and a powered air-purifying respirator having at least one filter and a blower and having an output connected by a hose assembly to the facepiece. A control interface operationally connects the self-contained breathing apparatus to the powered air-purifying respirator. The self-contained breathing apparatus includes a pressure vessel, a cylinder valve assembly and a pressure reducer, all carried by a back frame, and the powered air-purifying respirator is adapted to be mounted on, and carried by, the back frame, by coupling the back frame and the respirator together at respective attachment points.

Abstract: A powered air-purifying respirator that includes an enclosure, defining a single contiguous enclosed interior, an inlet duct, including an inlet and a distribution portion, that guides ambient air to the interior of the enclosure, a plurality of filter canisters disposed within the interior of the enclosure, and a blower that forces air through the at least one inlet, into the interior of the enclosure and through the plurality of filter canisters to produce filtered air suitable for breathing. A valve controls the flow of ambient air through the inlet duct. A fluid dam, disposed in an air path between the inlet and the filter canisters prevents liquids from reaching the filter canisters. The enclosure is reinforced and is adapted to provide protection for the filter canister from flame and heat while the filter canister is in use. A recirculation valve recycles previously-filtered air back into the enclosure.