Face masks and respirators frequently leak as they do not readily adjust to fit all sizes and shapes of heads. For workers with eyeglasses, beards, mustaches or long hair, a tight seal is almost impossible. The protective helmet on the other hand protects the head, nose, eyes, mouth, ears and respiratory system. Weighing from 2 to 4 pounds, the helmet is molded of fiberglass usually with a double shell to give air distribution to the face area. Suspension on the head is from an adjustable band.
Some manufacturers provide a chin strap to help stabilize the helmet so that it moves with the head.
Wide angle vision is provided through a clear face shield. Made of tough polycarbonate, the shield is abrasion resistant and impact proof. Air is supplied to the helmet through a flexible hose from a blower unit that is worn on a belt. Air flow is regulated with several motor speeds on the blower. Helmet models for greenhouse application operate on battery power.