🔍 Key Concepts

• Self-contained vs. supplied-air systems – where does the breathing gas come from? • Protection in an unsafe / toxic atmosphere vs. only specific gases • Mobility and ability to move anywhere on the vessel without being tied to a hose or fixed source

💭 Think About

• Ask which option lets the wearer move freely without being connected to anything else and still have breathable gas. • Consider which device is designed for a wide range of hazardous atmospheres, not just one specific gas. • Think about whether all three listed devices can handle any unknown or oxygen-deficient atmosphere, or if some are limited-purpose.

✅ Before You Answer

• Check which device has its own independent air or oxygen supply carried by the wearer. • Verify which options depend on a fixed external source of fresh air through a hose. • Confirm which option(s) are designed for general toxic or oxygen-deficient atmospheres, not just a single chemical.