The complete Emergency Response Guidebook (current version is 2008, it's updated every 4-5 years) is available for download at: http://www.phmsa.dot.gov/staticfiles/PHMSA/DownloadableFiles/Files/erg2008_eng.pdf It has the meanings of the various symbols and codes, and also recommended evacuation distances (and hazmat requirements).
Emergency Medicine - saving the world from themselves, one at a time. "Thou shalt not be a victim, thou shalt not be a perpetrator, but, above all, thou shalt not be a bystander." I make the ADL soil themselves. And that makes me very happy 
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