This includes x-ray apparatus, radiotherapy linear accelerators, and particle accelerators. Ionizing radiation is a much broader category than radioactivity alone, as many non-radioactive sources also emit potentially dangerous levels of ionizing radiation. The sign is commonly referred to as a radioactivity warning sign, but it is actually a warning sign of ionizing radiation. The standard does not specify the radiation levels at which it is to be used. It is not used for non-ionizing electromagnetic waves or sound waves. It may be used to signify the actual or potential presence of ionizing radiation.
The standard specifies the shape, proportions, application and restrictions on the use of the symbol. In 1974, after approval by national standards bodies, the symbol became an international standard as ISO 361 Basic ionizing radiation symbol. It was first documented as an international symbol in 1963 in International Organization for Standardization (ISO) recommendation R.361. The symbol was adopted as a standard in the US by ANSI in 1969. The trefoil is black in the international version, which is also used in the United States. The original version used in the United States is magenta against a yellow background, and it is drawn with a central circle of radius R, an internal radius of 1.5 R and an external radius of 5 R for the blades, which are separated from each other by 60°. This resulted in the background being changed on the radiation hazard sign. Blue was typically used on information signs and the color tended to fade with weathering. However, a blue background for other signs started to be used extensively. 2225) was chosen because it was expensive and less likely to be used on other signs. The shade of magenta used (Martin Senour Roman Violet No. At the time, it was rendered as magenta, and was set on a blue background. It first appeared in 1946 at the University of California, Berkeley Radiation Laboratory. The international radiation symbol is a trefoil around a small central circle representing radiation from an atom.
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