Code of Federal Regulations Title 49. Transportation § 49.392.50 Ignition of fuel;  prevention

(a) Fuel a commercial motor vehicle with the engine running, except when it is necessary to run the engine to fuel the commercial motor vehicle;

(b) Smoke or expose any open flame in the vicinity of a commercial motor vehicle being fueled;

(c) Fuel a commercial motor vehicle unless the nozzle of the fuel hose is continuously in contact with the intake pipe of the fuel tank;

(d) Permit, insofar as practicable, any other person to engage in such activities as would be likely to result in fire or explosion.