We investigate the influence of polar gases on the electric resistance of oriented thin films of pentacene, cobalt phthalocyanine, cobalt chloride phthalocyanine, and methyl red organic dye obtained by thermo-vacuum deposition. It is determined that, under the action of ammonia and ethanol, a decrease of the electric resistance of thin films will be in progress by 10(3)...10(5) times at a stable response signal and will give the possibility to use a simplified construction of gas sensors as a result of the absence of the heating of elements. The investigated films may be used as sensitive elements of gas sensors in the processes which accompany the ethanol evolution or for monitoring the product freshness by the pressure of ammonia which evolves from proteins during the products go bad.