Provided is a sample dish for detecting microbes. The sample dish includes a base having an opening extending therethrough, an outer side wall at the outer periphery of the base, and an inner side wall at the inner periphery of the base defined by the opening. The sample dish may be used in conjunction with a microbial test unit including a housing defining an internal cavity configured to contain a sample dish, the unit including a cuff extending from an outlet of the housing into the internal cavity. The cuff may be an open-ended member configured to extend through an opening of the sample dish and provide fluid communication between the internal cavity and the outlet. The microbial test unit provides the ability to test compressed gas directly input to the unit.