🔍 Key Concepts

• Confined space entry testing order: oxygen, flammables, then toxics • Difference between an oxygen indicator and a combustible gas indicator • Normal safe oxygen range in air (about 21% oxygen)

💭 Think About

• Ask yourself: What is the FIRST and most basic thing you need to verify before entering any confined space? • Which instrument is used specifically to check for explosive gas levels, and how is that different from an oxygen indicator? • Do any of the choices describe a measurement that doesn’t match the name of the instrument given in the question?

✅ Before You Answer

• Verify which choice focuses directly on oxygen level rather than flammable gas or CO2. • Check that the description matches how you’d test a tank or hold for safe breathing levels before entry. • Eliminate any option that mainly describes lower explosive limit (LEL) or CO2, since those are usually separate instruments or sensor modes.