Warning Signs for Seven Main Groups of Hazardous Substances

Written by david mcguffin
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Warning Signs for Seven Main Groups of Hazardous Substances
Trucks transporting hazardous materials must be clearly labelled. (Thomas Northcut/Photodisc/Getty Images)

Internationally, there are different ways that governments use to classify and label hazardous substances. The seven main groupings of hazardous materials, introduced by the Hazardous Materials Transportation Act of 1975 describe the dangers of each material while it is in transport. In addition to regulating the placards that are placed on each vehicle transporting hazardous materials, other required information also includes shipping papers, package markings and package labelling.

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Hazardous Substances Groups

Hazardous substances are grouped according to the worst case scenario of that particular substance coming into contact with an individual or if the substance becomes unstable in any way. There are seven groupings of hazardous substances including harmful, dangerous to the environment, corrosive, flammable, explosive, toxic and oxidising. Additionally there are subcategories for some of the categories that can measure toxic materials as "very toxic" and flammable materials as "extremely flammable."


For safety data sheets, there are seven symbols for the categories of hazardous substances. A skull and crossbones designates a "toxic" substance, however, if there is a "T+" in the upper-left corner, the substance is "very toxic." An "X" designates a "harmful" substance, however, if there is a lower-case "i" on the bottom-right of the "X," then it is known as an "irritant." A fire symbol describes a "highly flammable" substance, with the addition of a "F+" designating a chemical that is "extremely flammable." An "explosive" substance is symbolised by a ball with shards and fragments exploding outwardly. A dead tree and upside down fish designates a chemical that is "dangerous to the environment." Oxidising substances are designated by a circle with flames on top of it. Beakers with drops falling on a board or hands designate a "corrosive" substance.


Danger symbols, described in the previous section, appear as black signs and symbols overlaid on an orange background and are shaped as a square. The symbols and signs for these substances and chemicals are to be easily visible on shipping and storage containers as well as transportation vehicles for each of these substances. Additionally there should be a safety data sheet and specific information describing the hazardous substance placed near the symbol or sign.

International Symbols

According to Control of Substance Hazardous to Human Health, there are new international symbols, since 2009, that do not have any word-based descriptions. These nine symbols are enclosed in a red diamond shape, with some of the symbols having identical or similar resemblance to the seven hazardous materials symbols including toxic, dangerous to the environment, oxidising and corrosive. The chemicals safeguarded by the international symbols are described on the packaging and the safety data sheet that is transported with the information describing the specific hazard.

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