HazMat Placards

What do all the numbers and symbols on those diamond HazMat placards mean? (Other than STAY REALLY REALLY FAR AWAY!) Some signs are different colors, and which chemical compound is a 1207? A 750? And where can I get a list to keep in the car so I know what I’m sharing the highway with (or might be all over the highway any moment).

Lessee if I remember right. I know the colors - red means flammability hazard, blue is health hazard, and yellow is volatility, I think - that is, the ease with which it evaporates. Each diamond has a number from 0 to 4. The higher the number, the bigger the danger in that area.
The white diamond is kind of a miscellaneous slot. That’s where you stick other information, like “reacts with oxygen.” I don’t know all the codes for that diamond, though.

I think that’s mostly right. Hope it helps.

UN1207 = hexaldehyde
UN0750 does not exist according to this hazmat book.

Basically, every hazardous material has a UN number. Some chemicals with similar properties share a number. If a trailer is placarded with the UN number displayed, it either means that the material in question is in containers whose volume exceeds 119 gallons, or that there is more than 8,000 of that material with no other shipments on the trailer.

If a trailer is placarded without the number, it means that over 1,001 lbs. of that class of hazmat is on the trailer. Dangerous placards mean that two or more different classes of hazmat with weights totalling over 1,001 lbs are loaded together. The other class placards (e.g. Flammable, Poison, Oxidizing material, Spontaneously Combustable) are pretty much self-explanatory.

I’m sure the DOT’s site would have detailed explanations of all the classes and subclasses.

Hazardous Materials Transportation Placards


You’re thinking of labels on freight and (IIRC) MSDS’s. Trailer placards are a totally different animal.

Should have read 8,000 lbs.

Oops, should have clarified more. I forgot about the ones on bottles and such (there usually is/supposed to be a hazardous materials binder available near these).

I mean the removable diamond placards seen on tractor-trailers and tanker trucks transporting chemicals, gasoline, and such, where there is no HazMat binder nearby. The number is usually 3 or 4 digits, and there is a symbol, either a little flame (flammable/ inflammable?) or a what looks like an oxygen tank. Some have a green background, red background, or yellow background. These are the ones I want to know.

Dang, you people are WAY too fast! I just looked at the topic review and I’ve got answers before typing my clairifications. (Stiches are out next week and back to two-handed typing!)

Thanks! I’ll check this out and give the trucks a wide berth.

Green - Non-flammable gas

Red - Flammable liquid, flammable solid, flammable gas, or spontaneously combustible

Yellow - Oxygen, Oxidizer, Organic Peroxide, Radioactive (don’t worry; you’ll see a little three-bladed radioactive symbol on these. I’ve rarely seen them on the road anyway)

Orange - Explosive

Blue - Dangerous when wet (Scary when you think about it)

White/Black - Poisons, infections substances, corrosive.

If you’re looking for information on which UN numbers stand for which substances, you’ll have to find yourself a hazmat book. Or ask me. I have one here at work. I’m sure there’s an online resource with this information, but you’ll probably have to do a little bit of digging.

The book you’re thinking of is the North American Emergency Response Guidebook (NAERG). It’s supposed to be carried in the glovebox of every emergency vehicle in the US. The book gives a listing of all United Nations numbers (UN Numbers), those are the 4 digit numbers in the center of the placards. Each number represents a certain product or products. Those numbers cross reference to the product name, and to a “guide” in the back of the book. Each guide gives initial emergency information regarding that product. I say product since not all of the UN Numbers are for chemicals (self-inflating life vests and battery powered wheelchairs have UN Numbers).

Lucky for the OP, the NAERG 2000 is online:

The site kind of explains how to use the ERG. If you can’t figure it out (which I’m sure you can, its not that difficult), let me know…if I can teach firefighters how to use it, anyone else should be easy :).