In the European structural codes, a limit state design concept is used. Ultimate limit states (ULS) and serviceability limit states (SLS) are considered, as well as durability and, in the case of buildings, fire resistance. Partial safety factors are included in both design loads and material strengths, to ensure that the probability of failure (i.e., not satisfying a design requirement) is acceptably low. Members are first designed to satisfy the most critical limit state, and then checked to ensure that the other limit states are not reached.