Respirator inhalation and exhalation valves open and close opposite each other to maintain a constant, neutral pressure inside the mask. Inhalation valves open when a worker breathes in to allow air to flow freely into the mask through the filters. Exhalation valves close automatically when the inhalation valve opens. They open when workers breathe out to release breath and moisture from the mask, making masks to make them more comfortable by reducing eyewear fogging. For use with 5400 Series Respirators, 5500 Series Respirators. 7600 Series Respirators and 7700 Series Respirators.