🔍 Key Concepts

• stack emissions color and cause in marine boilers • relationship between air-fuel ratio and combustion products • how unburned fuel vs excess air typically appear (black vs white smoke)

💭 Think About

• Think about what normally causes white smoke from a boiler or diesel stack: is it usually incomplete combustion, excess air, or something else? • Consider what happens when you greatly increase the amount of combustion air to a burner while keeping the same fuel rate. • Ask yourself which of the listed conditions could realistically occur at the same time in a properly operating boiler burner system.

✅ Before You Answer

• Identify which condition(s) would normally produce black or dark smoke, and rule those out for white smoke. • Consider whether excess air by itself would carry visible particles out of the stack. • Decide if all of the above can be true at the same time, based on your understanding of complete vs incomplete combustion.