Fixed temperature-sensing elements of the fusible metal alloy type shall be replaced at least __________ from the date of installation.

• A. Semiannually
• B. Quarterly
• C. Monthly
• D. Annually

Answer: (A)

The fixed temperature-sensing elements using fusible metal alloy are intended to melt at a specific temperature to release the extinguishing agent. Over time they can age, corrode, or drift due to heat cycling and environmental exposure, which can affect their reliability. To ensure the system actuates promptly when needed, these elements must be replaced at least every six months from the installation date. Shorter intervals (monthly or quarterly) would be more frequent than required and add unnecessary maintenance, while longer intervals (annual) could allow performance drift beyond acceptable limits. Replacing at six months keeps the system’s response predictable and reliable.