: Weathering test of various safety helmets were conducted in order to obtain data to decide the helmets' working life, because plastics, from which safety helmets are made, deteriorate through weathering. In addition the properties of plastics do not necessarily indicate the performance of the helmet, and there is little data concerning this subject.
    Three types of safety helmets, called ABS, PE1 and PE2, were tested. ABS's shell is made from acrylonitorile-butadiene-styrene and shells of PE1 and PE2 were made from polyethylene. They were exposed to the sun and rain from 12 to 30 months, and were tested in several manner.
    First they were inspected visually. The changes in appearence were small for PE1 and PE2, but the appearance of ABS that were exposed longer than 12 months had deteriorated noticebly.
    Then they were tested in accordance with the regulations for shock absorption and penetra tion. Because a change of the regulations were expected, both old and new test methods were used. In addition to the regulation tests, tests in more severe conditions were also conducted. These were shock absorption test in very low temperature, penetration test with a higher falling height, and so on.
    In a shock absorption test using a hemispherical striker, test pieces of ABS that were exposed longer than 15 months failed, that is, due to contact between the helmet and the dummys' head impact load exceeded the permissible limit. Test pieces of PE1 and PE2 that were exposed for 15 or 24 months showed sympotum of deterioration in a low temperature shock absorption test. The connection point between the shell and hammock of PE1 broke, and the hammock of PE2 broke in the test.
    In a penetration test of a whole helmet, ABS helmets that were exposed longer than 12 months failed and showed manifest symptoms of deterioration, that is, the striker touched the dummys' head or it broke part of the shell and made a hole.
    In a penetration test of shell, 21 and 27 months exposed PE2 failed, that is, penetration depths were over the limit (10 mm). 18 and 21 months exposed ABS also failed.
    In conclusion, all type of helmet showed some symptoms of deterioration. With respect to the regulations ABS deteriorated clearly, whilst PE2 showed signs of deterioration and PE1 showed no deterioration.