A unified filter and connector housing (24) incorporating a diversion valve assembly (74), the housing assembly being usable with a protective breathing mask assembly (12) of the type requiring separate breathing gas and ventilating gas supply lines (18 and 20). The housing assembly includes first and second housing members (26, 32) which receive therebetween a filter (30) in an airtight relationship. The first housing member is provided with inlets (46, 62) to which quick disconnect supply lines (50, 66) for breathing gases and ventilating gases may be secured. Parallel breathing and ventilating gas passageways (42, 58) are disposed within the first housing member, only the breathing gas passageway normally being in a fluid communication with the filter. The diversion valve assembly (74) is operatively disposed between the breathing and ventilating gas passageways (46, 58) and when disposed in an emergency position opens the communication between the two passageways while substantially blocking the ventilating gas passageway downstream of said opening to cause most of the gas received from either inlet to flow through the filter and into the breathing gas supply line (18) and permitting only a small portion of the gas received from either inlet to pass through the ventilating gas supply line (20).