🔍 Key Concepts

• Review how air doors are typically located on a boiler furnace front or burner assembly • Notice which numbered parts are flat, plate-like pieces that pivot to open/close air flow • Compare the left cross‑section view with the right front‑view to match the parts that control combustion air

💭 Think About

• On this illustration, which numbered parts appear to swing or pivot over an opening to regulate air entering the burner? • Look closely at the right‑hand circular view: which components look like paired doors or flaps rather than valves, linkages, or casings? • Which choice numbers (1, 3, 9, 4) are pointing to parts that clearly affect air flow and are not shafts, housings, or indicators?

✅ Before You Answer

• Be sure the part you pick is shown as two similar plates or flaps that can open and close • Confirm that the part is on the air side of the burner, not on the fuel line or mechanical linkage • Verify that the number you choose is pointing to the door surfaces themselves, not to the operating mechanism or surrounding casing