What's Wrong with This Picture? Sunlight and extreme heat can damage a hard hat and compromise it's protectiveness. To make matters worse, damage from heat and sunlight is often invisible to the naked eye and only becomes apparent when the hard hat is tested under "battle conditions." Of course, that's the worst time to learn about a defect in protective equipment. The moral: Make sure you warn your employees to store their hard hats in a cool, dark place.