After each reading of an oxygen indicator,...

🔍 Key Concepts

• Oxygen indicators are used to measure the percentage of oxygen in a space before entry • After using any gas-detection instrument, you want to be sure it gives an accurate reading for the next measurement • Think about what kind of gas (or mixture) would safely clear out any remaining sample and leave the instrument ready to measure a new space

💭 Think About

• Which option would help prevent contaminating the next reading with leftover gas from the previous sample? • Which gas or mixture is safest and most commonly available on board for preparing instruments for the next test? • Would any of the choices themselves affect or distort an oxygen reading if left inside the instrument?

✅ Before You Answer

• Make sure the purging medium will NOT alter oxygen readings by adding or removing oxygen unnaturally • Confirm that the choice is non‑corrosive and safe for the instrument components • Check which option would be readily available everywhere on the vessel, regardless of which compartment you are testing

After each reading of an oxygen indicator, the instrument should be purged with __________.

CO2

water

the tested compartment's air

fresh air