What is the correct procedure to safely jump-start an EMS vehicle?

• A. Disconnect negative leads first, then connect the positive leads; start recipient and donor in sequence; remove cables in any order.
• B. Start both engines before connecting cables.
• C. Connect positive leads first between donor and recipient, then connect the negative lead to a solid engine ground away from the battery, start the donor then the recipient, and remove cables in reverse order; ensure both engines off during connections if required.
• D. Reverse order: connect negative to engine block first, etc.

Answer: (C)

The essential point is doing jump-starts with a safe, controlled sequence to prevent sparks near the battery and to ensure a solid electrical path for starting the EMS vehicle.

Connecting the positive leads first between donor and recipient establishes the circuit without creating a direct short to ground. Then attaching the negative lead to a solid engine ground away from the battery provides a safe return path and keeps any sparking away from the battery where hydrogen gas could be present. Starting the donor vehicle first supplies the necessary cranking power, and starting the recipient afterward allows it to use that power to crank and start without stressing either electrical system.

When removing the cables, doing so in reverse order minimizes the risk of sparks or stray currents causing a short, especially while the system is still energized. Detaching the negative from the recipient, then the negative from the donor, followed by the positive from the recipient, and finally the positive from the donor helps ensure the circuits are broken safely.

If your procedure calls for keeping engines off during connections, follow that guidance, but the described sequence remains the safest and most common practice.