Over-exposure to the sun is of course bad for your skin, but that's not the only thing adversely affected by its rays. Man-made materials like plastic will slowly degrade when left out in the sun, so 3M has developed a new line of hard hats featuring a color-changing UV sensor that tells the wearer their head protection might not actually be so safe.

Hard hats are designed to deflect and absorb the impact of objects falling from above, but as they're exposed to sunlight for long periods of time the plastic can become brittle. So instead of protecting the wearer's head, they have a higher risk of just shattering, which of course provides no protection at all. And instead of just guessing if a hard hat is still ok, the red UVicator sensor on the front of 3M's new $14 models slowly fades to white—like a reverse sunburn—as an obvious indicator it's time to swap out your head gear. [3M via Gear Patrol]