Heat detectors that must be replaced after actuating are ___.

• A. one-shot
• B. disposable
• C. non-restorable
• D. one-and-done

Answer: (C)

Some heat detectors are designed for single-use: after they actuate, they can’t be reset and must be replaced to return the system to normal operation. When the sensing element is triggered, the internal mechanism is permanently altered, so attempting to reset could leave the detector unreliable or cause a false alarm. That’s why this type is described as non-restorable—the device is considered spent after actuation and needs a new unit to restore protection. The other terms are informal or less precise; non-restorable is the standard way to express that a unit cannot be reused after it has operated.