A symbol prescribed by the Code of Federal Regulations. It is a magenta or black trefoil on a yellow background. It must be displayed where certain quantities of radioactive materials are present or where certain doses of radiation could be received
Centers for Disease Control and Prevention, Emergency Preparedness and Response, Radiation Emergencies, Radiation Dictionary, U.S. Department of Health and Human Services, Atlanta, GA, USA 2011. http://emergency.cdc.gov/radiation/glossary.asp, (Dzstr/ Rad Emr - Amer) {820}