🔍 Key Concepts

• Safe entry procedures for enclosed/confined spaces such as tanks • Required oxygen percentage for safe human entry and work • Why continuous or repeated testing is needed even after ventilation

💭 Think About

• Think about what can happen to gas levels in a sealed tank over time, even after it has been opened and ventilated. • Consider what the minimum safe oxygen level for breathing normally is compared with the percentages mentioned in the choices. • Ask yourself whether a simple gas mask is enough protection if oxygen is too low or toxic gases are present.

✅ Before You Answer

• Verify the minimum safe oxygen content usually required for entry into a tank or confined space (compare it to 14% and 12%). • Check which option mentions ongoing or repeated testing rather than a one‑time test or no test. • Make sure you understand that low oxygen is a life‑threatening hazard that cannot be solved by just a simple gas mask.