If your job calls for wearing a hard hat, wear it--there's never a good excuse not to. Areas where potential head hazards exists include anywhere there's a danger of falling, walking into objects, being exposed to falling or moving objects or bumping into exposed electrical wires--and anywhere there is a posted "Hard-Hat Area."
A quick guide to hard hats
Choose the right hard hat. All are designed to protect you from falling objects, and some are specifically designed to help protect you from electrical shocks.
Ensure the hat sits comfortably and securely on your head by adjusting the suspension system. This system acts as a shock absorber, while the outer shell resists blows to the head. The hat shouldn't fall when you bend your head forward, nor should you wear it tilted back on the head.
Look closely at the suspension, watching for cracks or tears, frayed or cut straps and other signs of wear.
Also, if your hard hat is made of a thermoplastic, such as polyethylene or polycarbonate, inspect the shell for stiffness, brittleness, fading, dullness of color or a chalky appearance. If the shell or suspension shows any of these conditions or if it is otherwise damaged, ask your employer to replace your hat.
Treat your hat properly to maintain its impact resistance. This means:
Don't drill "air holes" in the shell, or scratch or engrave into its surface.
Don't use paints or adhesives on it.
Do apply adhesive decals or reflective plastic tape for working at night, but never use metal tape, which can conduct electricity.
Don't expose the helmet to extreme heat or ultraviolet light from the sun by leaving it on the dashboard or rear window of a vehicle, for example. UV light is a hard hat's worst enemy. Although UV inhibitors are added to some hard hats, any hat is susceptible to deterioration from UV light over time. If your work puts you in lots of sunlight, make sure you replace your hard hat more frequently.
Regularly clean the hat, including its sweatband and its cradle with warm, soapy water, and rinse thoroughly; hair oils and dirt can weaken the shock-absorbing suspension system. Never use solvents.
Never carry or wear anything inside your hard hat between the suspension and the shell. For the hat to work properly, there needs to be clearance between the shell and your head. A ball cap or other object may limit this clearance. An object placed under the hat may also contain metal parts that can reduce your protection against electrocution.