🔍 Key Concepts

• combustion efficiency in auxiliary boilers • effects of air-fuel ratio on soot formation • relationship between burner condition and incomplete combustion

💭 Think About

• Which option would most directly lead to incomplete combustion and unburned carbon (soot) in the furnace? • Which factors mainly control flame quality: fuel pressure, burner condition, firing cycle, or contaminants in fuel? • Think about which choice would cause poor atomization, dirty flame tips, or misaligned air registers.

✅ Before You Answer

• Identify which choice most clearly affects air-fuel mixing and flame shape. • Eliminate any option that mainly affects pressure or cycling but not combustion completeness. • Focus on the answer that is most closely tied to dirty burners, misadjustment, or lack of cleaning.