About UN numbers and hazard classes
What is a UN number?
A UN number is a four-digit code that identifies a dangerous substance or article in transport. It is assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods and is used worldwide on shipping papers, package markings and vehicle placards. Gasoline, for example, is UN 1203.
What is the difference between a UN number and an NA number?
NA (North American) numbers are assigned by the U.S. Department of Transportation for materials that need a U.S.-specific entry, such as NA1993 for combustible liquids. They are recognized in the United States and Canada but not for international shipments, which use UN numbers.
Where do I find the UN number?
On shipping papers it appears with the proper shipping name and hazard class. On packages it is marked near the shipping name, and on tank trucks, rail cars and bulk containers it is shown on an orange panel or on the placard itself.
1203What does n.o.s. mean?
N.o.s. stands for “not otherwise specified”. These are generic entries, such as UN 1993 Flammable liquids, n.o.s., used for substances that have the right hazard but no entry of their own.
What are packing groups?
Within most classes, substances are also given a packing group by degree of danger: I for great danger, II for medium danger and III for minor danger. The packing group decides how strong the packaging must be. One UN number can have several packing groups.
How do I read a hazard placard?
The diamond's color and symbol show the hazard, and the number in the bottom corner is the class or division. Red means flammable, green non-flammable gas, yellow oxidizer, white with a skull toxic, black and white corrosive. See all nine classes.
OSHA and DOT hazard classification
In emergency response, hazard classification usually brings to mind the U.S. Department of Transportation (DOT) and its Emergency Response Guidebook, used on arrival to identify the material involved. But classification starts with the Department of Labor's Occupational Safety and Health Administration (OSHA).
Under paragraph (d) of 29 CFR 1910.1200, OSHA's Hazard Communication Standard, “the chemical manufacturer or importer shall determine the hazard classes, and where appropriate, the category of each class that apply to the chemical being classified.” OSHA's classes, such as acute toxicity or flammable liquids, are graded by category, usually 1 to 4 or A to C, where 1 and A are the most hazardous. This is not the same as the NFPA 704 rating system, where 4 is the most hazardous.
DOT regulations parallel and extend OSHA's for materials in transport. A transportation incident is an extension of the manufacturing workplace, and DOT's nine hazard classes, set out in PHMSA's Emergency Response Guidebook and 49 CFR, follow the UN Model Regulations used around the world.