Question When refueling a vehicle carrying hazardous materials: Answers The engine should be left on. The engine should be turned off. The gas nozzle may be left unattended. Explanation If you need to refuel a vehicle carrying hazardous materials, you must first turn off the engine. While refueling, someone must be at the nozzle and controlling the fuel flow at all times. Take a FREE Practice Test Now This questions appears in the following tests: California HazMat , Iowa HazMat , Maine HazMat , North Carolina HazMat , Ohio HazMat , Rhode Island HazMat , Washington HazMat , Wyoming HazMat ,