A safety system for a pressure vessel comprising: a poppet housing with a poppet slidingly mounted therein, wherein the poppet is configured to close a flow path through the poppet housing in a first poppet position, and to open a flow path through the poppet housing in a second poppet position; and a bracket operatively connected to the poppet housing and configured for mounting to a support structure ; characterised in that the system further comprises: a safety pin slidingly mounted in the poppet housing , wherein the safety pin is configured to block movement of the poppet in an extended position, and to allow full movement of the poppet in a retracted position; and an actuation lever operatively connected to actuate the safety pin between the extended and retracted positions, wherein the bracket includes a safety mechanism configured to release the actuation lever to maintain the safety pin in the extended position with the bracket not mounted to a support structure , and to force the actuation lever to allow the safety pin to move to the retracted position with the bracket mounted to a support structure , wherein the safety mechanism includes a yoke slidingly engaged to the bracket for movement between a first position releasing the actuation lever to maintain the safety pin in the extended position, and a second position to force the safety pin to move to the retracted position, wherein the safety mechanism includes one or more positioning pins mounted to the yoke and extending through the bracket with the yoke in the first position if the bracket is not mounted to the support structure and for being pushed in toward the bracket , moving the yoke to the second position with the bracket mounted to the support structure . a poppet housing with a poppet slidingly mounted therein, wherein the poppet is configured to close a flow path through the poppet housing in a first poppet position, and to open a flow path through the poppet housing in a second poppet position; and a bracket operatively connected to the poppet housing and configured for mounting to a support structure ; characterised in that the system further comprises: a safety pin slidingly mounted in the poppet housing , wherein the safety pin is configured to block movement of the poppet in an extended position, and to allow full movement of the poppet in a retracted position; and an actuation lever operatively connected to actuate the safety pin between the extended and retracted positions, a safety pin slidingly mounted in the poppet housing , wherein the safety pin is configured to block movement of the poppet in an extended position, and to allow full movement of the poppet in a retracted position; and an actuation lever operatively connected to actuate the safety pin between the extended and retracted positions, wherein the bracket includes a safety mechanism configured to release the actuation lever to maintain the safety pin in the extended position with the bracket not mounted to a support structure , and to force the actuation lever to allow the safety pin to move to the retracted position with the bracket mounted to a support structure , wherein the safety mechanism includes a yoke slidingly engaged to the bracket for movement between a first position releasing the actuation lever to maintain the safety pin in the extended position, and a second position to force the safety pin to move to the retracted position, wherein the safety mechanism includes one or more positioning pins mounted to the yoke and extending through the bracket with the yoke in the first position if the bracket is not mounted to the support structure and for being pushed in toward the bracket , moving the yoke to the second position with the bracket mounted to the support structure . <EOS>