Which safety device confirms that a flame exists when the burner starts in an oil furnace?

The correct answer is that a flame sensor confirms the existence of a flame when the burner starts in an oil furnace. The function of a flame sensor is crucial for the safe operation of the furnace, as it detects the presence of a flame to ensure that the burner is functioning correctly. If a flame is not detected, the sensor will typically trigger a safety mechanism to shut down the fuel supply, preventing the risk of unburned oil accumulating, which can lead to dangerous situations such as explosions or carbon monoxide buildup.

While an electric spark igniter may initiate the flame, it does not confirm its presence. Similarly, a cadmium sulfide photo-cell is used mainly in photovoltaic applications and is not relevant in this context. An oil safety valve plays a role in controlling the flow of oil but does not confirm whether a flame has ignited or is maintained. Therefore, the flame sensor’s role is essential as it provides critical feedback on the operational status of the furnace, ensuring safety and efficiency.