Helmets can only protect when retained on the head, therefore, a chin strap may be supplied to ensure retention in typical workplace conditions. EN 397 requires that either the helmet shell or the headband is fitted with a chinstrap or with the means of attaching one, i.e. anchorage points. Any chinstrap supplied must have a minimum width of 10 mm when un-tensioned and be attached either to the shell or to the headband.
The strength of the strap anchorage(s) should be sufficient to enable any attached chin strap to hold the helmet on the head but not so great that the strap would become a strangulation hazard. In the method for measuring chin strap anchorage strength specified in EN 397 the helmet is mounted onto a suitably sized headform and the chin strap passed around an artificial jaw. A tensile force is then applied to the artificial jaw at a rate of 20N/min until the artificial jaw is released, due to failure only of the anchorage(s). The standard requires that the force at which this occurs shall be no less than 150 N and no more than 250 N.