Do You Have to Kill the Power?
A Chief Officer is asking some challenging questions about powering down a vehicle's 12-volt electrical system at a crash scene.
Below are his questions and my reply. How would you answer this if you were a fire officer and someone in your department asked these questions?
"As a chief I am looking for a more professional opinion on this matter. On "typical accidents" that involve entrapment or confinement how important is it to de power a vehicle. Does it "have to be done"?
Powering down the 12-volt power on a vehicle involved in a crash is important but the situation at hand does have to be taken into consideration.
If the crash-damaged vehicle is unoccupied, then a fire department officer on-scene can decide if anything needs to be done to the 12-volt electrical system of the vehicle at all. If in doubt, the officer should have a crew open the hood normally and disconnect both the ground and the hot cables from the vehicle's battery.
If EMS personnel are going to be working with a patient inside the vehicle, the fire/rescue team officer should then assign a crew to the electrical system shutdown. Disconnect the 12-volt power cables if they is readily accessible. The crew can 'double cut' the cables to shut down the power if access to the battery is obstructed. This is justified due to the risk posed to responders from items such as undeployed airbags for example.
I recommend that anytime a fire/rescue crew commits vehicle rescue tools to a vehicle for extrication tasks, the electric system of that vehicle should be shut down prior to their work. Ripping off a door, cutting a roof, moving the dash, etc, are all tasks that you do not want arcs, sparks, or electrical shorts to occur during the work.
Shutting down a 12-volt electric system is a four-step process;
1_ Locate Battery
2_ Disconnect or 'Double Cut'
3_ Pull plugs from cigarette lighter ports
4_ Confirm 12-volt power shutdown