In an earlier letter written in 1948, Garden explained why this particular shade of magenta color was selected: 'it was distinctive and did not conflict with any color code that we were familiar with. The first signs printed at Berkeley had a magenta (Martin Senour Roman Violet No. This event was described in a letter written in 1952 by Nels Garden, head of the Health Chemistry Group at the Radiation Laboratory: 'A number of people in the group took an interest in suggesting different motifs, and the one arousing the most interest was a design which was supposed to represent activity radiating from an atom.' The three-bladed radiation warning symbol, as we currently know it, was 'doodled' out at the University of California Radiation Laboratory in Berkeley sometime in 1946 by a small group of people. The Office of Civil Defense originally intended fallout shelters to use the radiation warning symbol with the circle in the center and the three blades, but this idea was rejected because a fallout shelter represents safety whereas the radiation warning symbol represents a hazard. The general form is very similar to the above however there is no central circle. The civil defense symbol for a fallout shelter consists of a circle divided into six sections, three black and three yellow. The radiation warning symbol should not be confused with the civil defense symbol designed to identify fallout shelters. Paul Frame, Oak Ridge Associated Universities

Fallout shelter 1950 symbol