According to the Motorcycle Safety Foundation and the Snell Memorial Foundation, motorcycle helmets should be replaced every five years.
How Helmets Work
Helmets generally have four elements: a hard outer shell, an impact-absorbing liner, retaining system and comfort padding. The outer shell and liner operate by spreading the energy of an impact to reduce the amount of energy transmitted to the wearer's brain.
Why Replace a Helmet?
The length of time that a helmet is viable was determined by a consensus between the helmet manufacturers and the Snell Foundation. Hair oils, body fluids, environmental situations and normal wear and tear may cause a deterioration in performance. The Snell Foundation also advises that protective advances in the helmet technology also changes within five-year periods.
Any helmet that was involved in an accident should be replaced immediately, as some or all of it's shock absorption qualities may have been used. Older helmets, though they may appear to be in good shape, may have worn or frayed chin straps or hidden cracks.
Should a Dropped Helmet be Replaced?
In most cases, your helmet is still good. Most manufacturers offer an inspection service and may, at their discretion, repair the helmet. The Snell Foundation recommends that if you suspect your helmet is compromised, then replace it. If the helmet has been involved in an impact while in use, replace it.
What is the Snell Foundation?
Founded in 1957, the Snell Memorial Foundation was formed in an effort to promote research, education, testing and development of standards geared to improve the effectiveness of automotive racing helmets.
William Snell was an amateur sports car race driver who was killed in a crash in 1956. He died of massive head injuries when the helmet he was wearing failed to protect his head.