Hot surface ignition makes use of a _______ carbide ignitor that heats up to a red hot condition.

• A. Graphite
• B. Silicon
• C. Tungsten carbide
• D. Silicon carbide

Answer: (D)

Hot surface ignition relies on a material that can heat up to a red-hot surface quickly and survive the high-temperature, oxidizing environment inside a gas furnace. Silicon carbide fits this need best: it’s a ceramic that can reach very high temperatures, holds up under continuous heating, and maintains its emissive surface in the presence of heat and fuel. When current flows through a silicon carbide ignitor, it glows hot enough to ignite the gas-air mixture.

Graphite would oxidize and burn in air, so it isn’t reliable for a red-hot ignition surface. Silicon alone doesn’t withstand the high temperatures needed for ignition. Tungsten carbide isn’t used as the heating element in this context because it doesn’t provide the same combination of high-temperature emissivity and oxidation resistance as silicon carbide.