Disposable respirators and dust masks protect workers from harmful dust particles. Some disposable respirators and dust masks have adjustable nose clips that increase comfort, provide a tighter seal and prevent eyewear fog. Others have a valve that releases hot air and moisture from inside the mask to keep workers cool in hot environments. Disposable respirators and dust masks are used only once. They are ideal in applications that produce a lot of dust such as sanding, grinding and agricultural harvesting. They do not protect against oily mists.