Hazard symbols or warning symbols are recognisable symbols designed to warn about hazardous or dangerous materials, locations, or objects, including electric currents, poisons, and radioactivity. The use of hazard symbols is often regulated by law and directed by standards organisations. Hazard symbols may appear with different colors, backgrounds, borders and supplemental information in order to specify the type of hazard and the level of threat (for example, toxicity classes). Warning symbols are used in many places in lieu of or addition to written warnings as they are quickly recognized (faster than reading a written warning) and more commonly understood (the same symbol can be recognized as having the same meaning to speakers of different languages).
The biohazard symbol is used in the labeling of biological materials that carry a significant health risk (biohazards), including viral samples and used hypodermic needles.
The biohazard symbol was developed by the Dow Chemical Company in 1966 for their containment products.
According to Charles Baldwin, an environmental-health engineer who contributed to its development: "We wanted something that was memorable but meaningless, so we could educate people as to what it means." In an article in Science in 1967, the symbol was presented as the new standard for all biological hazards ("biohazards"). The article explained that over 40 symbols were drawn up by Dow artists, and all of the symbols investigated had to meet a number of criteria: "(i) striking in form in order to draw immediate attention; (ii) unique and unambiguous, in order not to be confused with symbols used for other purposes; (iii) quickly recognizable and easily recalled; (iv) easily stenciled; (v) symmetrical, in order to appear identical from all angles of approach; and (vi) acceptable to groups of varying ethnic backgrounds." The chosen scored the best on nationwide testing for memorability.
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