🔍 Key Concepts

• Automatic boiler combustion control sequence during startup and shutdown • Purpose of a post‑purge or pre‑purge cycle in boiler operations • Safety reasons for delaying burner ignition after shutdown

💭 Think About

• What dangerous condition could exist inside the furnace immediately after a shutdown if you tried to relight the burner too quickly? • Which step in the automatic sequence must be completed before it is safe to introduce fuel and ignition again? • Among the choices, which one directly improves safety in case unburned fuel or vapors are left in the furnace?

✅ Before You Answer

• Identify which option deals with clearing the furnace or combustion chamber itself, not auxiliary equipment. • Eliminate options that relate mainly to normal operating parameters (like water level) rather than ignition safety. • Confirm that the correct choice is the one that removes any residual combustible mixture before relighting.