🔍 Key Concepts

• Span gas vs zero gas (what each is used for in gas detection systems) • How fixed and portable gas analyzers are checked for accuracy before use • Difference between calibrating an instrument and purging/inerting a space

💭 Think About

• Ask yourself: when you hear the word span, does it sound more like setting a scale, setting the zero point, or changing the tank atmosphere? • Think about what you must do to a gas analyzer so you can trust the readings before entering a potentially dangerous space. • Which answer choices describe changing the instrument’s behavior, and which describe changing the tank’s atmosphere?

✅ Before You Answer

• Identify which options talk about the instrument (gas analyzer) versus the tank or atmosphere. • Distinguish between setting the zero point and setting the measurement scale or reading on an analyzer. • Eliminate any choices that describe gas-freeing, purging, or inerting tanks, since those are different processes from span gas use.