Thick Inner Lining Helmets should have about 1-inch of firm polystyrene foam. It may not be visible, but you should be able to feel the thickness. If the helmet only contains soft foam padding or no padding at all, then it is a unsafe helmet.
Sturdy Chin Strap and Rivets The DOT safety standard includes strong chinstraps and secure rivets.
Weight of Helmet An unsafe helmet will weigh a pound or less. Your safe helmet should be around three pounds.
Design/Style of Helmet An unsafe helmet will have any protruding attachments/decorations that will extend further than two-tenths of an inch from the helmet's surface (with the exception of visor attachments).
DOT Sticker A helmet that meets or exceeds the Federal Motor Vehicle Safety Standard 218 will have a DOT sticker on the outside back of the helmet. Beware of novelty helmets sales, which may sell DOT stickers separately. In this case, the DOT sticker is invalid.
Snell or ANSI Label Private and/or non-profit organizations such as Snell or ANSI will place labels on the inside of the helmet, stating the helmet meets their safety standards. In addition to the DOT stickers, these are good indicators that the helmet meets all required safety standards.
Manufacturer's Labeling Under the FMVSS 218, manufacturers are required to label their helmets with their name, the model, the size and the month/year of manufacture. It must also state the construction materials and space for the owner to list their information.