How does a Firesafe valve work?

The Firesafe™ Cannula Valve/Firesafe™ Nozzle comprises a spring loaded valve probe contained within a moulded housing. In normal condition the valve is held open by means of a T‐bar arrangement on the valve probe at the downstream end that sits on a fusible ledge. The valve is actuated when the fusible ledge softens as a result of the heat from an approaching fire in the oxygen tubing.