In many chemical reactions, reactive radicals have been shown to be transient intermediates. The free radical character of a chemical species is often, but not always, indicated by adding a superscript dot to the chemical formula. A consistent use of this radical symbol on all species that have radical character is suggested. Free radicals have a spin quantum number of 1/2 and the allowed changes of the net spin quantum number (s) are 0, [plus or minus]1, [plus or minus]2, ... in any transformations including chemical reactions. By applying this simple rule and a consistent use of a radical symbol on all radical species, the construction of chemical reaction equations and the reaction mechanism of radical reactions can be clarified. The examples of decomposition of water and cyclohexane molecules induced by high-energy photons or ionizing radiation and the example of the complex reactions taking place during the irradiation treatment of flue gases are used to demonstrate these suggestions. (Contains 1 table, 2 figures and 2 schemes.)