🔍 Key Concepts

• Supplied-air vs. self-contained breathing apparatus (SCBA) and how long each can provide breathable air • The difference between filter-type masks (that clean existing air) and devices that bring their own air or oxygen • How continuous flow versus demand (on inhalation) systems affect duration

💭 Think About

• First decide which devices actually work in an oxygen-deficient space, not just a smoky or toxic environment. Which options would fail if there is almost no oxygen in the space? • Among the devices that DO bring their own breathable gas, which setup is likely to have the largest practical supply and therefore the longest safe working time? • Consider whether the air/oxygen source is portable and limited or comes from a remote, larger supply that is not carried on the back.

✅ Before You Answer

• Eliminate any option that only filters or purifies ambient air instead of supplying its own breathable gas; those cannot work in oxygen-deficient spaces. • Focus on which device can be connected to a large external source of air rather than just the amount you can carry with you. • Verify which systems are typically used for extended work periods in confined or oxygen-deficient spaces in maritime/industrial safety practice.