Wipe off the hard hat daily with a damp cleaning rag to remove loose dirt and dust.
Add a few drops of mild laundry detergent to the damp rag and rub over the hat to remove heavier buildup.
Wash the sweat band by hand. This sweat band typically pops off of the hat's interior. Fill the sink with warm water and a few drops of laundry detergent, and dip the sweat band into the soapy water. Scrub the sweat band with your fingers, rinse, wring out and allow to air dry.
Snap the sweat band back into place when it is fully air dried.