A pressure relief apparatus for venting a tank comprising: an inlet port ; an outlet port ; a closure member retained, relative to the inlet and outlet ports, for preventing, or substantially preventing, fluid communication between the inlet port and the outlet port ; a trigger mechanism including a temperature responsive portion ; wherein: the trigger mechanism and the closure member are cooperatively configured such that the closure member becomes released from retention and moveable for effecting establishment of fluid communication between the inlet port and the outlet port in response to receiving of heat energy by the temperature responsive portion ; characterized in that the pressure relief apparatus further comprises: a compartment for receiving pressurized fluid from the outlet port and communicating the received pressurized fluid to the trigger mechanism; wherein: the trigger mechanism , the closure member , and the compartment are cooperatively configured such that the closure member becomes released from retention and moveable for effecting establishment of fluid communication between the inlet port and the outlet port in response to the communication of the pressurized fluid to the trigger mechanism via the compartment . an inlet port ; an outlet port ; a closure member retained, relative to the inlet and outlet ports, for preventing, or substantially preventing, fluid communication between the inlet port and the outlet port ; a trigger mechanism including a temperature responsive portion ; wherein: the trigger mechanism and the closure member are cooperatively configured such that the closure member becomes released from retention and moveable for effecting establishment of fluid communication between the inlet port and the outlet port in response to receiving of heat energy by the temperature responsive portion ; characterized in that the pressure relief apparatus further comprises: a compartment for receiving pressurized fluid from the outlet port and communicating the received pressurized fluid to the trigger mechanism; wherein: the trigger mechanism , the closure member , and the compartment are cooperatively configured such that the closure member becomes released from retention and moveable for effecting establishment of fluid communication between the inlet port and the outlet port in response to the communication of the pressurized fluid to the trigger mechanism via the compartment . the trigger mechanism and the closure member are cooperatively configured such that the closure member becomes released from retention and moveable for effecting establishment of fluid communication between the inlet port and the outlet port in response to receiving of heat energy by the temperature responsive portion ; characterized in that the pressure relief apparatus further comprises: a compartment for receiving pressurized fluid from the outlet port and communicating the received pressurized fluid to the trigger mechanism; wherein: the trigger mechanism , the closure member , and the compartment are cooperatively configured such that the closure member becomes released from retention and moveable for effecting establishment of fluid communication between the inlet port and the outlet port in response to the communication of the pressurized fluid to the trigger mechanism via the compartment . a compartment for receiving pressurized fluid from the outlet port and communicating the received pressurized fluid to the trigger mechanism; wherein: the trigger mechanism , the closure member , and the compartment are cooperatively configured such that the closure member becomes released from retention and moveable for effecting establishment of fluid communication between the inlet port and the outlet port in response to the communication of the pressurized fluid to the trigger mechanism via the compartment . <EOS>