Termination Steps H H H H H A reaction is classified as a termination step when any two free radicals join together producing a nonradical compound. Combination of free radical with contaminant or collision with wall are also termination steps. Chapter4 9Chapter 4 9 Termination Steps • A reaction is classified as a termination step when any two free radicals join together producing a nonradical compound. • Combination of free radical with contaminant or collision with wall are also termination steps