Where are the identification numbers assigned to chemicals located? Question Where are the identification numbers assigned to chemicals located? Answers In the DOT Emergency Response Guidebook (ERG) In the truck's manual On the EPA’s website Explanation The four-digit identification numbers assigned to specific hazardous chemicals are listed in the U.S. Department of Transportation (DOT)'s Emergency Response Guidebook (ERG). This questions appears in the following tests: California HazMat