Radiation Hazard Symbol

Submitted by Roland Roberts on Mon, 11/13/2017 - 14:27

The traditional radiation hazard symbol is the black trefoil with a yellow background, shown below. This symbol is generally accompanied by text describing the specific nature of the radiation hazard. This is only to be used for ionizing radiation hazards. Non-ionizing radiation and laser radiation have different warning symbols.1

According to Radiation Emergency Medical Management web site:

  • International symbol of radiation, usually accompanied by more specific text.
  • Symbol can be magenta or black, on a yellow background.
  • Sign must be posted where radioactive materials are handled or where radiation-producing equipment is used.
  • Sign is used as a warning to protect people from being exposed to radioactivity.

While not mentioned, you will sometimes see a similar, but not identical, symbol older building which were designated as fallout shelters.

Other Related Hazard Symbols

There is a wikipedia article on Hazard Symbols which has several standard symbols which may be of interest, including the symbol for non-ionizing and laser radiation.

History of the Radiation Symbol

The original symbol was designed at the University of California in Berkeley and used a magenta symbol on a blue background. The choice at that time was partially due to cost (it was expensive to make and thus wasn't going to be used frivolously) and partially due to the fact that those colors were not used in anything else and so would stand out.2 But the blue background tended to fade easily, especially outdoors. After some experimentation, the design settled on the current sign, albeit with a magenta symbol, as being the most easily seen and identified.