🔍 Key Concepts

• Confined space testing procedures (what must be checked before entry) • Limitations of an oxygen indicator (what it can and cannot measure) • Effects of contaminant gases (like CO2 and flue gases) on sensitive instruments

💭 Think About

• Think about why we sample at more than one level in a confined space. What changes from top to bottom? • Ask yourself: Does an oxygen indicator measure all gases present, or just one specific thing? • Consider whether combustion products (like flue gases) and CO2 might interfere with sensitive measuring devices or be completely harmless to them.

✅ Before You Answer

• Verify what an oxygen indicator is actually designed to measure (oxygen only, or other gases too?). • Recall standard confined space entry procedures: do we test just one level or multiple levels, and why? • Consider whether exposure to other gases (CO2, flue gas, hydrogen) can cause errors, damage, or limitations in an oxygen indicator.