🔍 Key Concepts

• Self-contained breathing apparatus (SCBA) air flow path: cylinder valve (mainline valve) → regulator → bypass valve → facepiece • Purpose of a bypass valve: when and why it is used (emergency use, regulator failure, low-pressure situations) • Relationship between bypass valve and mainline (cylinder) valve—which one actually turns the air supply on or off at the bottle

💭 Think About

• Think about what happens to the air supply if the mainline valve is shut while you try to use the bypass valve. Would air still reach the user? • Consider why the bypass valve exists: Is it meant to replace the mainline valve or to temporarily route air in a different way? • In an emergency, would you want to create an extra step or risk accidentally stopping your air supply while using bypass?

✅ Before You Answer

• Verify which component actually controls the primary on/off for the air in the SCBA: the cylinder (mainline) valve or the bypass valve. • Confirm whether the bypass valve can deliver air if the cylinder valve is not supplying pressure to the system. • Check standard SCBA operating procedures for emergency use: what is done with the mainline valve before opening the bypass?