A contaminant is a substance present in small amounts in other chemicals. If the sensitivity of a reaction to such substances present in reactants is very high, then a runaway reaction can occur
Safety 2 Safety S2S - A Gateway for Plant and Process Safety, The European Web Portal for Process Safety, USA 2003. http://www.safety-s2s.eu/modules.php?name=s2s_wp4& idpart=4&op=v&letter=all, (IndS - Amer) {458}