You're about to load Division 1.1 explosives onto your trailer. What does federal regulation require regarding the vehicle's engine during this process?

49 CFR 177.835(a)

Loading explosives is one of the highest-consequence tasks a hazmat driver performs. A running engine adds vibration, heat, and electrical ignition sources right next to sensitive cargo. Requiring the engine off removes that risk during the exact window when packages are being handled and are most vulnerable.