Which sound indicates metal has been softened by heat and pressure and may signal risk of BLEVE?

• A. Pinging
• B. Humming
• C. Clanging
• D. Ringing

Answer: (A)

Pinging is the sound that shows metal is yielding under heat and internal pressure. When a pressurized vessel containing flammable liquid or gas is heated, the metal walls can soften and deform as stress builds. That sudden, sharp, high-pitched tapping—pings—signals the wall is weakening and a BLEVE could be imminent if heat continues. The other sounds don’t carry the same warning: humming is typically facility or equipment noise, not an indicator of structural change; clanging comes from pieces striking each other and isn’t tied to wall weakening; ringing is a steady tone that can occur in many situations and doesn’t specifically reflect a vessel losing strength. Because pinging directly points to metal softness and impending failure under heat, it’s the best warning of BLEVE risk. If you hear it, increase distance, evacuate if needed, and alert responders.