When should a crew call for car 10-50 during a fire incident?

The appropriate moment for a crew to call for car 10-50 during a fire incident is when arson is suspected. This is because car 10-50 is typically designated for investigative purposes related to suspicious fires. When a crew suspects that a fire has been intentionally set, it is critical to have specialized resources that can assess the situation, gather evidence, and work in conjunction with other authorities to ensure a thorough investigation.

In this context, the other options don't align with the specific situational requirements that trigger the activation of car 10-50. For example, while fire in the vicinity or a need for evacuation are important considerations during firefighting operations, they do not necessarily indicate that arson is involved. Instead, they would require different protocols and resources focused on emergency response and safety rather than investigation. Additionally, calling for car 10-50 only during training exercises would undermine its purpose in active scenarios where real determinations of arson are vital to public safety and legal proceedings.