How to Read an NFPA 704 Diamond – Part 4


The white square – at the bottom of the NFPA diamond – is different from the other three squares. It doesn’t contain a number. Instead, it contains one of three “special hazard” symbols. These are hazards that cannot be defined by the ratings in the other three squares.

Materials that react violently or explosively with water earn the “water reactive” symbol, a W with a horizontal line through it:


Materials that act as oxidizers will have the “oxidizer” symbol: OX .

Simple asphyxiant gases – nitrogen, helium, neon, argon, krypton, and xenon – will have the “simple asphyxiant” symbol: SA .

If a material is both water reactive and an oxidizer, the “water reactive” symbol is to be displayed in the special hazards (white) square of the NFPA diamond, and the “oxidizer” symbol is to be displayed either directly below or adjacent to that square.


So now you know how to read an NFPA diamond!


DISCLAIMER: This article is designed to promote understanding

of the NFPA rating system. It is not a complete explanation of

the criteria involved.

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HCL Labels assists hundreds of Fortune 500 companies in managing their GHS Chemical Label Library.

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NOTICE: New Requirements for Pharmaceutical Labels in California

Important Notice Regarding all Pharmaceutical Labels in the State of California.

According to the 2017 Medical Waste Management Act, Section 118275, (1)(6)(B), all Pharmaceutical labels in California are required to be updated with a specific change.

HCL Labels will be updated all of our pharmaceutical waste labels to remain consistent with the update. The change states that pharmaceutical waste that is prepared for transportation shall not be labeled with the word “Pharmaceutical,” but instead with the words “Incineration Only” or “High Heat.

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Should you have any questions regarding this regulatory update, please email us at

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HCL Labels is capable of high-end custom digital printing with the printers we have in our Scotts Valley office.

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