During a fire, what happens in an oxygen cylinder safety valve to prevent an explosion?

The correct answer explains a critical safety feature of oxygen cylinders designed to prevent the risk of explosion during a fire. When exposed to high temperatures, the increased pressure within the cylinder can become dangerous. To mitigate this risk, a safety disc or rupture disc within the valve is set to activate at a specific, predetermined pressure threshold. If the pressure exceeds this level due to heat, the disc ruptures, allowing oxygen to be released safely and slowly, rather than allowing the pressure to build up to explosive levels. This design helps ensure that the gas can escape in a controlled manner, reducing the likelihood of an explosion and enhancing overall safety during a fire situation.

Understanding this mechanism is essential in welding and industrial environments, where oxygen cylinders are commonly used and can pose a significant hazard under stressful conditions.