49 CFR 173.56 specifies the process which must be followed in obtaining DOT approval for the commercial shipment and transportation of explosives.

For all explosives except those produced by the U.S. Department of Defense or the U. S. Department of Energy, new explosives must be examined and assigned a recommended shipping description, classification, and compatibility group by an agency authorized by the Associate Administrator to do so. This examination and recommendation involves a 5-step process.

The Office of Special Permits and Approvals, within PHMSA's Office of Hazardous Materials Safety, processes the applications, relying on evaluation of the supporting data by scientists in the Office of Technology.

When an application is approved, a formal Classification of Explosives letter is sent on behalf of the Associate Administrator advising of any limitations or special requirements which must be observed, and assigning an "EX Number" signifying that the new explosive is approved for transportation in commerce.