Safety

Safety is a property of a system which permits the system to operate without dangerous consequences for people (including serving personnel) and the environment. For many systems (as aircraft, submarines, chemical plants, nuclear power stations, etc.), some kinds of failures can lead to catastrophic results. In these cases, the safety indices coincide with reliability indices after the choice of the appropriate criteria for defining failure. These might be the (complementary) probability of successful operation without accident, the mean time to accident appearance, and so on.

Sometimes, the safety of systems (as for dams of hydro-power stations, constructions in seismic zones, etc.) is considered to be only under the influence of nature. In this case, probabilistic measures may be insufficient and one should instead consider conditional safety under some specified levels of external influence.

But many systems may be harmful even under ideal conditions, without accidents. Examples are...