The National Fire Protection Agency (NFPA) has rules for identifying dangerous materials in section 704 of the National Fire Code. Here you can order blank diamond signs and labels, numbering kits and guides that are made in the USA.
NFPA diamond signs give essential hazard information to emergency responders and people who handle dangerous chemicals
Refer to NFPA Standard 704 Section 4.3, Location of Signs, for specifics on where to post NFPA 704 placards
Any facility that uses or stores large amounts of hazardous chemicals in the U.S. must use diamond signs and labels