This Gulf standard specifies the symbol to be used to signify the actual or potential presence of ionizing radiation and to identify objects , devices, materials or combinations of materials winch emit ionizing radiation . For the purposes of this standard , ionizing radiation includes gammas and X-rays, alpha and beta particles , high-speed electrons , neutrons , protons and other nuclear particles ; but not sound or radio waves , or visible , infra-red, or ultraviolet light . This standard does not specify the radiation levels at which the symbol is to be used .