🔍 Key Concepts

• Combustion air supply and why burners need the correct air-fuel ratio • How incomplete combustion changes flame color and shape • Typical appearance of a properly adjusted burner flame vs. one that is starved for air

💭 Think About

• Think about what happens to fuel if there isn’t enough oxygen: does it burn cleanly or leave unburned products? How would that look in a flame? • Which choice suggests soot, smoke, or unburned carbon rather than a clean, hot burn? • Compare the colors mentioned: which sounds like a cooler, dirtier flame instead of a hot, efficient one?

✅ Before You Answer

• Identify which option best matches signs of sooting or carbon formation (black smoke, streaks, or deposits). • Recall that a hot, efficient flame is usually blue to bright yellow and sharply defined – eliminate any option that sounds too clean or hot. • Ask: which description would an engineer associate with insufficient air and incomplete combustion, not just flame instability?