🔍 Key Concepts

• Backfire flame arrestor purpose – what type of fuel/engine can ignite fuel‑air mixture in the intake if there is a backfire? • Differences between gasoline and diesel engine air/fuel systems on small passenger vessels • Where USCG/ABYC standards typically require flame arrestors for fire/explosion prevention in engine spaces

💭 Think About

• Which engine type is more likely to have a flammable fuel‑air vapor mixture in the intake that could ignite and travel back toward the fuel source? • Do diesel engines normally have a carburetor/throttle body with a fuel‑air mixture in the intake, or do they inject fuel directly into high‑pressure, high‑temperature air in the cylinder? • Would electric motors create an intake backfire risk similar to a fuel‑air internal combustion engine?

✅ Before You Answer

• Identify which choice(s) involve flammable fuel‑air vapors in an intake system (vs. direct fuel injection or no fuel at all). • Confirm from your study materials which engine type on small passenger vessels is specifically mentioned in connection with backfire flame arrestors. • Eliminate any options that involve machinery that does not have combustion of a premixed fuel‑air charge in an intake manifold.