Why is displaying the hazmat ID number so important?

Column 4: Lists the identification number for each proper shipping name. Identification numbers are preceded by the letters UN or NA. The letters NA are associated with proper shipping names used only within the United States and to and from Canada. The identification number must now appear first on the shipping paper as part of the shipping description and also appear on the package. The identification number should always appear on cargo tanks and other bulk packaging. Police and firefighters use this number to quickly identify the hazardous materials.