What is the first step in using a fixed breathing air system on an aerial device?

The first step in using a fixed breathing air system on an aerial device is for responders to don a face piece with a special supply hose. This action is crucial because it ensures that the user is immediately prepared for the use of the breathing air system. Once the face piece is secured, the responder can then connect to the supply source, ensuring a proper fit and seal which is vital in maintaining the integrity of the air supply against contaminants.

In the context of safety procedures, donning the face piece first establishes a readiness for potential hazardous situations before making further connections or checks. This proactive measure helps protect responders' health and safety while they assess and prepare the rest of the system for operation.

Other steps such as connecting hoses or performing system checks follow after the individual is equipped with their protective gear. This order highlights the importance of personal safety as paramount in emergency scenarios where the breathing air system is to be utilized.