When using the oxygen indicator, which...

🔍 Key Concepts

• How an oxygen indicator cell works (it consumes oxygen chemically or electrochemically from a small fixed sample) • Difference between an instrument’s response time and long‑term drift or temperature effects • What happens to the oxygen content inside the sample chamber after the sample is sealed and measured

💭 Think About

• Ask yourself: if the instrument uses up the oxygen inside a small fixed volume, will the reading stay where it is, or change over time? In which direction? • Think about whether the instrument should give a stable reading long enough for you to read it, or whether you’d expect it to keep moving as conditions change. • Consider which option describes a realistic, practical behavior for safe cargo tank testing in terms of getting a clear, trustworthy reading.

✅ Before You Answer

• Verify which choices describe the needle staying steady long enough to be read accurately. • Check which options involve the oxygen in the sample being consumed inside the instrument, and what that would do to the reading over time. • Eliminate any option where the reading is clearly unreliable or misleading for tank safety testing (e.g., obviously false due to temperature drift).

When using the oxygen indicator, which reaction from the needle should you expect as a sample is drawn into the instrument?

Rise to the correct reading and then, slowly fall to zero as the oxygen in the sample is consumed

Slowly rise to the correct reading and then remain stationary

Move back and forth and finally stabilize at the correct reading after about 10 seconds

Rise to the correct reading immediately and then rise slowly to a false reading as the operating temperature increases

🔍 Key Concepts

💭 Think About

✅ Before You Answer