Chemical Hazard Symbols and Their Meanings

Worked transporting hazardous material.
••• endopack/iStock/Getty Images

In the US, there are two main organizations behind the chemical warning symbols seen on hazardous substances: the Occupational Safety and Health Administration (OSHA) and the non-profit National Fire Protection Agency (NFPA). OSHA uses an array of symbols to convey the nature of a chemical hazard. The NFPA uses a multi-colored diamond design to achieve a similar goal.


From a flame to an exclamation point, OSHA's wordless pictograms are meant to convey the nature of the threat posed by a particular chemical. Each pictogram consists of a black symbol on a white background with a red diamond border. For example, the flame symbol means the chemical might be flammable, self-heating, self-reactive, an organic peroxide or it might ignite upon exposure to air. An exclamation mark means the chemical could be an irritant, skin sensitizer, toxic, a narcotic or hazardous to the ozone layer.


The NFPA uses only one symbol -- a four-sided diamond evenly divided into four smaller, colored diamonds that each contain a number or symbol. The top red diamond typically contains a number from 0 to 4, which represents a scale for a chemical's flammability. The left blue diamond contains a similar scale for toxicity. The right yellow diamond contains a scale for reactivity. Finally, the bottom white diamond is a space left for "special hazard" indicators, like one denoting that the chemical is a strong oxidizer or water reactive.

Related Articles

What Do the Colors Indicate on a pH Test Strip Paper?
Isopropanol Alcohol Vs. Isopropyl Alcohol
How to Make Bromine Water in the Chemistry Lab
How to Calculate Chemical Oxygen Demand
Sulfuric Acid & Chlorine Bleach Reaction
What Is Red Phosphorus?
What Is the Chemical Formula of Bleach?
Physical & Chemical Properties of Sodium Bicarbonate
Information and Facts on Opal & Moonstone
What Is Red Oxide Paint?
What Is the Meaning of a Black Ring?
How to Write a Chemical Compound Formula
What Are Yellow Diamonds?
Uses for Petroleum Coke
How to Get Colored Lighter Flames
How Does Neon Get Its Colors?
What Is the Gas Used in Neon Signs that Produces a...
What Does a Chemical Formula Represent?
What Is the Hardest-Known Metal?
How to Neutralize Food Coloring in Water