The semidisintegration period of Sayphos over tobacco leaves is determined--2.5 days at angular coefficient of the disintegration straight line K=0.12 1 ppm/ 1 mg/kg concentration of Sayphos over tobacco leaves is considered as harmless and accordingly safe for work. A table for minimal terms of safe work computation is also suggested. Because of the slow Sayphos decomposition in soil, the preparation should be employed but once--after the planting of tobacco.