Has the Helmet Been in a Crash?
If a helmet has been in a significant crash, it should be replaced. Many manufacturers offer "Crash Replacement Policies," offering new helmets at a discounted price when the crashed helmet is turned in. Even if you aren't in a crash but drop your helmet hard on a solid surface you should consider replacing the helmet. Any significant impact absorbed by the helmet may make it less effective the next time around.
How Old is Too Old?
Manufacturers recommend that a helmet should be replaced every three to five years, depending on usage and exposure to the elements. If you're unsure how old your helmet is, look for a sticker on the inside of the helmet that is marked with the original manufacturer's date. Manufacturers recommend replacing helmets every three to five years because exposure to the elements, sweat, and other factors like hair oils and sunscreen can degrade the protective foam inside of the helmet. When the foam is degraded it won't be as helpful at protecting your head in the event of a bicycle crash.
Does it Have a Cloth Cover or No Cover?
Bicycle helmet use and safety standards are a relatively new concept. The first, modern safety helmet for bicycling wasn't invented until the mid 1970's. It took another decade for the design of the helmet to really take shape. If you have a bicycle helmet with a cloth cover on the outside or no cover (just a foam outer shell), the helmet was made before 1984 and does not meet today's American National Standards Institute (ANSI) standard.
What Sticker is on the Inside?
Any helmet sold after 1999 must meet the US Consumer Product Safety Commission Standard (CPSC). If the helmet has an ATSM sticker (American Society for Testing and Materials), the standards are comparable and acceptable. Look for an ATSM, CPSC or Snell sticker on the inside of your helmet to confirm that it was designed to meet today's standards.
Has it Been Recalled?
If a helmet has been recalled it definitely needs to be replaced. Check the Bicycle Helmet Safety Institute website for a complete listing of helmets recalled by the U.S. Consumer Product Safety Commission. Bicycle helmets are recalled for a variety of reasons including strap failures and not meeting CPSC safety standards.
Inspect the Helmet Carefully
If the helmet is too small or too large, it will not give the protection it was designed to give. A helmet should fit snug and level on the head without a tilt and should not sit too low on the forehead. The chin strap on the helmet should fit securely against the bottom of the chin. This is especially important with children who are growing. Inspect the outside plastic and internal foam for cracking by pulling and squeezing the helmet. Inspect the chin strap for security and fraying.