Abstract: A bar is intermittently movable through an explosion sensing port in the wall of a chamber for cleaning the port without blocking it. The chamber is coupled to a mechanism for introducing a suppression agent into the chamber for suppressing or smothering an explosion within the chamber, and further has a pressure responsive device for actuating the explosion suppressing mechanism whenever the fluid pressure sensed through the sensing port reaches a predetermined value due to an explosion within the chamber. A duct fluidly connects the sensing port to the pressure responsive device, and the bar is movably mounted within a portion of the duct.