There is a call of a jumper and they are told to approach with the sirens turned off so as not to scare the jumper. However, they come out of the fire station with the sirens on. This is the correct procedure. Sirens are used when still far away from the scene because it's safer that way. They are then turned off within a certain distance from the scene.
When Gage and DeSoto start to pull the victim from the wrecked airplane, it's clear that there is nothing underneath the fuselage, but in the closeup as they start to run away, there is a shiny blue can that gives off an obvious spark just before the plane bursts into flames.