What is the proper order of internal atmosphere hazards to test before entering a confined space?

The correct order for testing internal atmosphere hazards before entering a confined space is to first evaluate the oxygen content, then assess for flammable gases and vapors, and finally check for potential toxic air contaminants.

This sequence is crucial to ensure safety during confined space entries. Testing for oxygen content first is essential because oxygen levels below 19.5% or above 23.5% can pose serious health risks, such as suffocation or oxygen toxicity. Ensuring a safe oxygen level is the foundation of entering any confined space safely.

Next, assessing flammable gases and vapors is vital to prevent fires or explosions. Flammable conditions should be evaluated after confirming that there is adequate oxygen, as the presence of flammable gases in an oxygen-rich environment significantly increases the risk of ignition.

Lastly, examining potential toxic air contaminants is important once the environment has been deemed safe in terms of oxygen levels and flammability. This helps to identify any harmful substances that might still be present in the space, allowing workers to take necessary precautions before entry.

Choosing this order prioritizes the immediate risks associated with entering confined spaces, facilitating a systematic approach to ensuring safety.