Safety symbols

About safety symbols

The collection begins with two families of hazard symbols. The GHS pictograms on chemical labels and safety data sheets are diamonds with a black symbol on a white background inside a red frame. Warning signs for biological, radiation, electrical and laser hazards are, in Great Britain, black symbols in a yellow triangle.

Three sections cover signs of other kinds. The NFPA 704 fire diamond, posted outside buildings, on doors and on tanks for emergency responders, rates a material’s health, flammability and instability hazards from 0 to 4. It is a square set at a point like a GHS pictogram, but holds numbers where the pictogram holds a black symbol. Safety signs in workplaces carry a signal word, such as DANGER in white on red or CAUTION in black on yellow, or a shape and colour, such as the red circle with a diagonal bar of a prohibition sign. Accessibility symbols, such as the sunflower lanyard, mark a need for help or time rather than a hazard.

Each page says what hazard a symbol identifies. What to do about it is on the product’s label and its safety data sheet, where the pictograms also appear.

A label or a sign?

The red-framed diamond belongs to the product: it is printed on the label of a hazardous chemical and on its safety data sheet, under the Globally Harmonized System of Classification and Labelling of Chemicals, which the United Nations developed to bring countries’ chemical rules into agreement. A warning sign belongs to a place or a thing: OSHA’s rules, for example, use the biological hazard warning to identify equipment, containers, rooms, materials and experimental animals that contain or are contaminated with hazardous agents.

Look-alikes between the two families

The skull and crossbones is the GHS pictogram for acute toxicity, GHS06. It is also part of the radiation warning the IAEA introduced in 2007, with radiating waves and a running person, placed on the housing of dangerous radioactive sources where it is seen only if someone takes the device apart. The biohazard symbol is not one of the nine GHS pictograms, but Canada’s WHMIS adds a pictogram of its own for biohazardous infectious materials. Within the GHS set, the flame means flammable and the flame over circle means oxidising.

Colours differ by country and regulator

Great Britain’s regulations draw biological risk, radioactive material, electricity and laser beam signs alike, black on yellow. In the United States each hazard has its own rules: OSHA’s biohazard labels are fluorescent orange or orange-red, and the Nuclear Regulatory Commission’s radiation symbol is magenta, purple or black on yellow. On US workplace chemical labels, OSHA uses eight of the GHS pictograms and treats the environment pictogram as optional.

Symbols that had to be learned

Charles Baldwin and Robert Runkle, reporting the biohazard symbol’s development in Science in 1967, wrote that there had been no universally used signal for infection hazards, and that the design was chosen for its uniqueness and memorability. The IAEA says the radiation trefoil has no intuitive meaning and little recognition beyond those educated in its significance.