Exposure of a metal ladder to a minimum temperature of approximately ______ will cause a heat sensor label to change colour.

• A. 121°C (250°F)
• B. 149°C (300°F)
• C. 66°C (150°F)
• D. 100°C (212°F)

Answer: (B)

Heat sensor labels on metal ladders are there to warn when the ladder has been exposed to heat high enough to potentially affect its strength. The label is designed to change color at about 149°C (300°F), a temperature at which heat can start to impact the ladder’s material properties and coating. This threshold is chosen so that the label reliably signals dangerous heat exposure while remaining stable under normal conditions. The other temperatures listed are too low to trigger the indicator in standard ladder materials, so they don’t provide the same safety cue. If the label has changed color, the ladder should not be used until it’s inspected and deemed safe.