<P> A hockey helmet is worn by players of ice hockey, inline hockey, and bandy to help protect the head from potential injury when hit by the puck, sticks, skates, boards, other players, or the ice . The shell of a hockey helmet is generally made of a substance called vinyl nitrile that disperses force from the point of contact, while the liner may be made of either vinyl nitrile foam, expanded polypropylene foam, or other material to absorb the energy, to reduce the chances of concussion . Hockey helmets grip the head from inside by cupping the back of head, or the occipital protuberance . Helmet manufacturers will have a chart that relates their helmet sizes to head measurements . Most helmets have tool - free adjustments, but on older models, the helmet size is adjusted by loosening the screws on the side to slide the front portion forward or back . </P> <P> A visor or face shield in ice hockey is a device attached to the front of a helmet to reduce potential of injury to the face . Visors cover the upper half of the face, while full face shields cover the entire face . A series of eye injuries, most notably that to Bruce Fogarty, have led to a call from many to enforce their wearing . As of 2015, 89% of NHL players wear visors . Many other leagues around the world mandate the use of visors . Visors and shields, made of a high impact - resistant plastic, offer better overall vision than the wire cages available, which can obscure vision in certain areas . The face shield provides excellent straight ahead and peripheral vision, but does not provide as good air flow as a cage . </P> <P> The American Hockey League, the top minor league in North America required all players to wear a visor prior to the start of the 2006--07 season . The NHL "strongly recommends" the use of visors . The NHL mandated visors in 2013, with an exception for players having 25 games experience . </P> <P> The hockey visor was first invented by Kenneth William Clay when he lost vision in his left eye to a high stick while playing for the Vanderhoof Bears . After a month in hospital in Vancouver, Clay created the first documented clear face shield in January 1964 . The invention caused quite a stir, with announcers calling it a "fish bowl" and a "wrap - around windshield". While the original shield and helmet were lost in the fire that consumed the Vanderhoof Arena a few years later, the newspaper clippings still attest to the dates and facts . </P>

When did visors become mandatory in the nhl