According to ÖNORM, the fire-retardant effect of materials is divided into several classes. EI230 and EI260 also belong to these fire resistance classes. The number in the designation indicates the minimum time the material can withstand a fire. For example, if a loft ladder is labelled EI260, it means that the staircase will prevent a one-sided fire from spreading further for at least 60 minutes. Fire-retardant attic stairs therefore save valuable time during rescue from a possible fire.