Applies to helmets of riders of motor bicycles and occupants of open motor cars, but does not apply to competition riding. This helmets are designed to mitigate the effects of a blow on the head received by a rider in the event of an accident. Test are given to ascertain compliance with shock absorption properties under various conditions of temperature an humidity, penetration resistance, regidity of the shell, strength of the harness and itsattachments, area to be protected.