A flow control device (20) and process are provided for controlling the flow of a pressurized fluid substance from a supply system (22). The device (20) includes a housing (30/40) that defines an orifice (84) for communicating between the supply system (22) that has an outlet end defining a discharge opening (57). The device 20 further includes a valve (140) having a flexible, resilient valve head (160) that has confronting, openable portions (186) movable from a closed configuration to an open configuration when the valve head (160) is subjected to a pressure differential acting across the valve head (160). The valve (140) is located across the housing outlet end discharge opening (57) so that the valve (140) and the housing (30/40) together define an expansion chamber (198) between the orifice (84) and the valve (140).