Based on the systematization of the experimental and epidemiological data on the toxicity of the compounds of mercury and cadmium and on the concept of a reasonable risk, the author has developed qualitative indices (criteria) required to analyze the safety of work associated with metallic mercury and cadmium at the dangerous industrial objects while declaring their safety. The fulfillment of these criteria ensures the high level of safety of mercury- and cadmium-associated work; it is in accord with the current trends in approaches to evaluating the safety of devices using toxically dangerous substances. The criteria considers the risk of human death due to the simultaneous intake of mercury vapors and cadmium oxide aerosols during accidents, as well as the level of chronic intake of these substances in different groups of persons on secondary dust formation (evaporation) after an accident.