Sure, you may feel virtuous every time you strap on your bike helmet, but even the sturdiest ones wear out over time, developing hairline cracks that aren’t always visible to the naked eye. But German scientists may have caught whiff of a new super-smelly detection method that tells you the instant you should give your noggin-protector the old heave-ho. As soon as damage occurs, odoriferous oils ooze from the plastic, alerting your nose in the rankest way possible that it’s time for a new helmet.


Because helmets are difficult to test for faults, cyclists can rarely tell when they’re in need of replacing. As a result, plenty of serviceable helmets get thrown out before their time, while many banged-up ones are unwittingly used for years. Here to the rescue: Researchers at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg and the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT in Oberhausen, who impregnated polypropylene with microcapsules of foul-smelling oils, then injection-molded the material into the final helmet shape. When stress is applied to the helmet, the resin-based microcapsules snap open, releasing an odor that gets stronger as the damage worsens.

When stress is applied to the helmet, the resin-based microcapsules snap open, releasing an odor.

This olfactory-based detection method has applications beyond cyclist safety, however. The stinky oils can also be injected into other products which are difficult to test for defects, including pressure hoses in washing machines and plastic water- and gas-supply pipes. Smell-detection could help indicate when materials are faulty or close to failure, potentially saving lives while minimizing damage from component breakdowns.

Now that’s something to smell about.

+ Crash Helmet With a Useful Smell

[Via ScienceDaily]