1.4.F Tobacco smoking.

f. Tobacco smoking. Aircrew members are discouraged from smoking tobacco at all times. They should especially refrain from smoking before flights at night and during all flights because smoking, with its increased carbon monoxide in the blood, results in greater detrimental physiological effects than would normally result from the altitude of the aircraft.

AR 40-8 * 17 August 1976 * Unclassified