A coupling for use with a blower unit for detecting leaks in a structure, wherein the coupling is constructed and arranged to attach to a surface of the structure defining an opening and to the blower unit, and to allow air flow through the coupling when the blower unit is attached to the coupling and to prevent air flow through the coupling when the blower unit is not attached to the coupling, and wherein the coupling further includes a pressure port defined within a surface of the coupling constructed and arranged to accommodate at least one of a differential pressure gauge fitting or a tube.