A vented gas riser for use in a system for conducting pressurized gas through a gas carrier pipe from a gas supply source line located below ground level to a delivery point disposed above ground is provided. A fluid tight gas riser protective casing is disposed around said carrier pipe and creates a gas escape passageway in an elongate annular space between the carrier pipe and the casing. A containment chamber is disposed below ground level which creates a confined space which has, as its only egress, a fluid connection to a gas escape passageway. Any gas which leaks into the containment chamber is directed into the gas escape passageway. A riser transition head, which includes at least one vent passageway, provides a fluid connection with said gas escape passageway and with the atmosphere such that any gas which leaks into said containment chamber is directed through the gas escape passageway and through the at least one vent and into the atmosphere.