The problem of ensuring occupational safety in the modern world is considered. It is related to the fact that the applied principle of hygienic rating, which is based on the determination of the limit values of each of production processes factors that have a harmful effect on the human body, does not ensure occupational safety. The main reason for this situation is the identification of the level of hazard using different systems of points and classes that are not metrologically justified. In addition, a person is always simultaneously exposed to the large number of factors, and it is almost impossible to consider all of them. One of the solutions to the problem is the application of risk theories. However, this approach does not provide for identifying the process regularity occurring in the human body under the influence of harmful factors, which does not allow to find the effective ways for occupational safety improvement.
To identify criteria for an objective quantitative assessment of occupational safety, the studies were carried out concerning the functioning of the human body as a nonequilibrium thermodynamic system. It obeys the law of the masses and the laws of thermodynamics of the biological systems for cases of physical labor in the malposition, heavy physical labor and stress psychological labor.
The research results showed that as a quantitative criterion for the hazard of labor, the time can be used of restoration of functional shifts caused by the influence of production factors, after their removal, during rest. Daily and weekly labor hazard factors are proposed. They characterize the level of functional shifts restoration during rest between the working shifts and for the weekend between working weeks. Labor is considered safe if these factors are less than one.