Ionizing radiation hazard sign

Ionizing (or ionising) radiation is radiation that carries enough energy to liberate electrons from atoms or molecules, thereby ionizing them. ... Gamma rays, X-rays, and the upper vacuum ultraviolet part of the ultraviolet spectrum are ionizing... Typical particles include alpha particles, beta particles and neutrons... Ionizing radiation arises from a variety of sources, such as ... the decay of radioactive materials, ... or acceleration of charged particles by electromagnetic fields... Ionizing radiation can also be generated by the production of high energy particles in X-ray tubes and particle accelerators. ... Ionizing radiation is invisible and not directly detectable by human senses, so radiation detection instruments such as Geiger counters are required. ... It is applied in a wide variety of fields such as medicine, research, manufacturing, construction, and many other areas, but presents a health hazard if proper measures against undesired exposure aren't followed. Exposure to ionizing radiation causes damage to living tissue, and can result in mutation, radiation sickness, cancer, and death. ... Radiation hazard warning signs. Hazardous levels of ionising radiation are signified by the trefoil sign on a yellow background. These are usually posted at the boundary of a radiation controlled area or in any place where radiation levels are significantly above background due to human intervention. [Ionizing radiation. Wikipedia]