When donning an air pack, what is the first thing you should check?

The first thing to check when donning an air pack is the unit itself. This involves visually inspecting the entire air pack for any obvious signs of damage or wear, ensuring that it is in proper working condition before use. This step is crucial as any malfunctioning or defective component could lead to failure during use, particularly in emergency situations where the air pack is critical for providing breathable air in hazardous environments.

Conducting a thorough check of the unit itself helps ensure its reliability and that it is ready for safe operation. It's important to verify that all parts are intact and functioning as intended before focusing on other elements like the air supply gauge, seals, connections, or the fit of the mask. Each of those components will be addressed after confirming that the air pack is fundamentally sound and operational.