A system includes a body, a sensor (50), a pressurized fluid source (46), and a blockage detection module (32). The body defines a cavity (44) open to an ambient environment at a port. The sensor communicates with the cavity to produce a signal representative of a fluid pressure within the cavity. The blockage detection module includes a pressure regulator (36) and a valve (38) disposed along a conduit (34) fluidly connecting the pressurized fluid source to the cavity. The blockage detection module includes a processor (40) and memory (42) encoded with instructions of a blockage detection method.