The yellow and black symbol below is a Trefoil. It is the international symbol used to warn people of a potential source of radioactivity and represents radiation being emitted from an atom. The trefoil symbol was first developed by scientists at the University of California, Berkley, in the 1940's.

Trefoil is derived from (Latin trifolium, three-leaved plant, French trèfle, German Dreiblatt and Dreiblattbogen ) is a term in Gothic architecture given to the ornamental foliation or cusping introduced in the heads of window-lights, tracery, panellings, etc., in which the center takes the form of a three-lobed leaf (formed from three partially-overlapping circles).




The International Atomic Agency (IAA) in 2007 unveiled a new warning symbol, due to the fact the symbol was not widely understood or recognised. The IAA sites that over the past two decades at least 20 people have died and 400 have been injured after accidentally exposing themselves to radioactive sources, such as radiography units that had been discarded in rubbish dumps.








To help reduce avoidable deaths the (IAA) unveiled a new symbol to label potentially fatal sources of radiation . Unlike the original, the new warning has been tested to ensure it was universally understood. The red background conveys danger, skull and crossbones and a trefoil emanating rays warns of a threat to human life, and a running man tells the observer to keep away.





Link to the website of the International Atomic Energy Agency