Why does soot reduce heating appliance efficiency?

• A. Reduces heat transfer
• B. Increases heat transfer
• C. No effect
• D. Increases fuel cost

Answer: (A)

Soot on the heat transfer surfaces acts as an insulating coating that lowers how effectively heat moves from the flame to the surrounding air. That insulating layer reduces radiant and, to some extent, convective heat transfer, so less heat actually reaches the space even though the fuel is burning. As a result, the appliance needs more fuel to achieve the same heating level, which shows up as higher energy usage. Keeping surfaces clean of soot restores the intended heat transfer rate and overall efficiency.