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What Do Those Diamonds on Flammable Liquid Containers Mean?

March 25, 2013
Hazmat Diamond

Hazmat characteristics are displayed in either a diamond or box

My job can be difficult to explain to people outside of the insurance industry. Whenever I meet someone new, they will invariably ask, “So, what do you do for a living?” Generally, I tell them that I inspect commercial properties for fire insurance companies. On one particular occasion, someone then followed up with, “What do those diamonds on flammable liquid containers mean?” The answer is a long one, but certainly helps to make my job quicker and easier.

As it ends up, the diamond symbol used on flammable liquid containers is a part of NFPA 704 and is not the same, nor does it mean the same thing, as the diamonds located on the back of trucks one might see on the freeway. What it does do is explain the Health (blue), Flammability (red), Instability (yellow), and Special Notice (white) of a particular container of liquids. It is used in industrial, commercial, and institutional facilities that may have hazardous materials on hand. By having a standardized method of conveying information, fire departments, emergency responders, and facility workers can be aware of the dangers of any particular material, or to clean-up any spills of the material. In a loss control inspection, it can be used to quickly help identify potential hazards of a risk.

The number within each color also corresponds to the level of severity on a scale of 0-4 (0 being the safest, 4 being the most dangerous), except in the bottom white section; in this instance, letters used correspond to special notices about the particular material.

The blue Health section is located on the left side of the diamond and is ranked from 0-4. 0 means it poses no health hazards (think water) whereas 4 would indicate that even a limited exposure could cause serious injury or death (think carbon monoxide).

The red Flammability section, located at the top of the diamond, tells anyone interacting with the liquid how flammable it is. 0 would indicate that the material is not going to burn (materials like carbon dioxide) and 4 would have a flashpoint below 73 degrees Fahrenheit.

Yellow, for Instability, on the right side of the diamond, indicates how stable or reactive a particular liquid is. A 0 would indicate that a particular material is stable, even in dangerous conditions (such as a fire), whereas a 4 would be explosive or easily detonated (nitroglycerin is a good example).

There are two symbols that NFPA 704 authorizes on the bottom white section of the diamond. The W (sometimes shown as W) indicates to fire officials and emergency responders that the chemical is unusually reactive with water and could become explosive if the fire is fought using water. Pure sodium, when exposed to water in large quantities, will have a tendency to explode (don’t mistake sodium with sodium chloride, which is common table salt and can be used, in conjunction with other materials, as an extinguishing agent in combustible metal fires like magnesium, sodium, etc.). The other approved symbol is OX and indicates that the hazardous material is an oxidizer. Hydrogen Peroxide, for instance, is an oxidizer. While not all oxidizers will necessarily explode when heated, they may contribute to the combustibility of other materials.

On occasion, other symbols are used in the white section of the diamond (“corr” indicates the material is corrosive), but the NFPA prefers to keep the symbols on the diamond simple, and corrosive or acidic hazards are already taken into account for in the health rating.

NFPA 704 isn’t just limited to describing the symbol for hazardous materials. It also specifies who can determine these codes for any particular material. The 2007 edition outlines where the signs should be placed within a facility and how to rate a chemical cabinet with numerous chemicals, along with other suggestions.

Article by: Kristen Skinner

Source: NFPA 704

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