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Why the NFPA diamond is priceless

nfpa diamond sign

In combination, this NFPA diamond and signage are effective in preventing accidental injury, and in informing workers at a glance on the nature of the hazards they face.

If you've ever seen a gas tanker drive by or gotten close to the storage facility in an industrial site, you might have spotted a yellow sticker with a multicolored diamond. That's the National Fire Protection Association (or NFPA) diamond, developed over the years to give workers an instant way to assess the dangers of working around hazardous substances.

Each quadrant of the diamond indicates a different set of dangers. The blue quadrant on the right indicates the level of health-risk, the red quadrant on top tells workers the danger of flammability, the yellow quadrant to the right indicates reactivity, and the white quadrant tells any special dangers that might not be implied by the other three sections.

(There's a special set of symbols designed specifically for this quadrant – a W with a horizontal slash through it indicates a water reactive substance, "Ox" means oxidizing agent, the skull-and-crossbones predictably mean poison, and the familiar trefoil means radioactivity.)

The three colored quadrants typically have a number from 0 to 4 in them, with 0 indicating "no danger" and 4 indicating the most hazardous compounds. As an example, the NFPA label for the strong organically based solvent acetone has a 2 in the blue square, 3 in the red square, 0 in the reactivity square, and nothing in the white square.

Trained workers will look at this diamond and recognize that acetone can cause injury and requires prompt treatment in case of contact; it can be ignited at all normal temperatures; but it's normally stable, and does not react to water. (Indeed, acetone exists naturally in the human body but can be harmful if it's ingested in large amounts – it's primarily dangerous because it's prone to sudden ignition at room temperature, and a spark can set a container of the solvent on fire if it contacts acetone vapors.)

Every chemical (and even some common mixtures) has its own agreed-upon ratings, which are occasionally updated to account for changing risk assessments. (Whale oil is a 0-1-0 chemical, while the fearsome chemical arsine gets a 4-4-2.)