An effectively worded warning conveys precise information concerning hazards. If the word "poison" appears on a bottle, most people know what it means. However, not everyone understands English. A French speaker might even mistake it for "poisson," the French word for fish. And some people cannot read and write. A universally understood symbol solves the problem. When a skull with two crossed bones appears on a bottle, the symbol effectively conveys the information that the contents of the bottle are poisonous.
Different countries have developed their own safety hazard symbols for chemicals. However, the United Nations has been promoting a globally harmonized system, or GHS, of hazardous chemical labeling, including standardized symbols. GHS attempts to give an exact description of hazards. For example, GHS still uses the skull and crossbones for poisons that are fatal or dangerously toxic when swallowed, inhaled or applied to the skin, but it uses an exclamation point if the poison is less dangerous. Such agencies as the U.S. Environmental Protection Agency are wrestling with the problem of changing their own established systems of symbols to conform to GHS.
Some chemicals can burst into flames, cause corrosion on contact, or react explosively when exposed to heat, water or air. Various symbols issue an appropriate warning. For example, in the United States, a red diamond with a picture of a flame and the word "FLAMMABLE" delivers a self-explanatory message. In the United Kingdom, a black and white flame on a square orange background issues the same warning. Also in the United Kingdom, the picture of a black, dead tree and a black, dead fish show that a chemical is dangerous to the environment. GHS uses the same symbol, but instead of the orange UK background, it has a white diamond-shaped background with a thin red border.
Traffic hazard symbols alert motorists to phenomena that might cause accidents. In the United States, road hazard symbols are fairly uniform from state to state. A picture of a deer on a diamond-shape yellow sign warns motorists to watch for deer. A red octagonal sign warns drivers to stop. If a symbol pictures a pair of children, a school zone is at hand. Other symbols mark the presence of a sharp curve, a steep hill or construction work.
A jagged lightning-like symbol warns of high voltage. Foods treated with radiation must display a radura, a picture of a green plant inside a nearly continuous green circle. The U.S. Occupational Safety and Healthy Administration has fabricated some interesting triangular hazard symbols, such as ice cracking under a man's weight to indicate thin ice.