Polarity 5 : The condition of having poles, or of being different, specially opposite, in properties or powers, or to form in opposite parts or directions, as the two electrodes of an electric cell, two ends of a magnet, etc. (Graham)
H. J. Porter (Chairman - Technical Committee), Dictionary of Fire Technology, The Institution of Fire Engineers, The Victory Press (Leicester) Ltd. 1979 UK. (Fr Tech - Brit) {81}