🔍 Key Concepts

• Complete vs incomplete combustion in marine boilers • Relationship between flame color/smoke color and fuel-air ratio • Effect of excess air or insufficient air on stack appearance

💭 Think About

• Think about what color the exhaust or haze would be if the fuel is burning cleanly with the right amount of air. • Consider which colors usually indicate soot, unburned fuel, or smoking conditions in a boiler furnace. • Ask yourself which option best represents minimal smoke and minimal unburned particles in the stack gases.

✅ Before You Answer

• Match each haze color with likely soot / unburned carbon content. • Decide which color suggests clean, nearly invisible exhaust rather than heavy smoke. • Eliminate any colors you associate with smoking, sooty, or dirty combustion.