The unit may or may not have an exhalation valve. The unit has no replaceable parts. Full facepiece Covers from roughly the hairline to below the chin. On the average provides the greatest protection, usually seal most reliably, and provides some eye protection as well. Fume respirators with replaceable filter Designed as respiratory protection against fumes of various metals having an air contamination level not less than 0.05 milligram per cubic meter.
Half mask Fits over the nose, mouth, and under the chin.
Hood or Helmet Loose-fitting respirators that enclose at least the head. A light, flexible device covering only the head and neck, or head, neck, and showers is called a hood. If rigid headgear is incorporated into the design, it is called a helmet. Blouses extend down to the waist, and some have wrist-length sleeves. The enclosure includes a system through which clean compressed air is distributed around the breathing zone.