When checking the aerial apparatus, which of the following should you do last?

When performing a pre-operation check on an aerial apparatus, it's essential to follow a sequence that prioritizes safety and operational readiness. Checking that all crew members have fastened their seatbelts is a vital safety procedure, but it should be done at the end of the checklist.

The sequence of operations typically starts with ensuring that the apparatus is in a safe and functional state. This includes observing the apparatus's gauges to assess engine performance, turning on the batteries to power the electronic systems, and disconnecting any auxiliary electrical and air sources which could interfere with the operation of the apparatus or pose safety hazards. Each of these steps is crucial for confirming that the aerial apparatus is ready for deployment.

Fastening seatbelts is vital for crew safety, but it is the final step in the process to ensure that everything else is in order before the vehicle is in motion. This way, you can confirm that all systems are operational and safe before securing the crew inside the apparatus for travel. Thus, completing the operational checks and systems verification first is the correct approach to ensuring both safety and functionality in a high-risk environment like firefighting.