A flame rod is used to ______.

• A. Detect flame failure
• B. Ensure the gas pilot is lighted
• C. Regulate fuel flow
• D. Purge combustion chamber

Answer: (B)

A flame rod is a flame-sensing element in gas-fired burner safety circuits. It sits in the flame and conducts a small current due to ionized gas, providing the control system with a signal that a flame is present. That signal keeps the gas valve energized so the pilot stays lit. If the flame goes out, the current drops and the control shuts the gas off to prevent unburned fuel from flowing. So the primary role is to verify that the pilot flame exists and maintain safe operation of the burner. This isn’t about regulating fuel flow, purging the combustion chamber, or acting as a separate flame-detection function outside the safety interlock.