To exclude irreversible biological effects establish a safe and regulated the maximum allowable levels or concentrations of energy or biological impacts. In determining the maximum permissible values have to make a choice between the probability of harm to human health and economic benefits of providing more stringent standards.
A threshold level of exposure risk exists for technical systems, building structures, mining facilities, etc. It is characterized by the ability of elements of technical systems, building structures, etc. to resist up to a certain limit and for a certain time, the negative (destructive) influences or useful (work) loads, while maintaining their intended function. This level is assessed qualitative and quantitative characteristics of the material elements or systems in General, referred to as reliability indicators.