A power semiconductor module including a housing within which lies at least one semiconductor switching element. The housing includes a vent aperture that is selectively openable and closeable by a cooperating vent cover. The vent cover is held in an open position during normal operation of the power semiconductor module to open the vent aperture and provide ventilation for the or each semiconductor switching element within the housing. The vent cover is urged into a closed position by an increase in pressure within the housing resulting from an explosive event inside the housing to close the vent aperture and inhibit the escape of explosion gases and/or debris from the housing via the vent aperture