This is an elastomeric respirator. These respirators provide the best protection and fit (other than units that provide a separate air supply, like SCBA (self-contained breathing aparatus) or PAPR (powered air-purifying respirator)). Elastomeric respirators are designed for reuse and the filters are replaceable. The most effective filters for these respirators are rated N100 or P100 (or P3 in Europe). The respirators usually have an exhalation valve to make breathing easier. If source control is desired, then the exhalation valve should be covered with separate cloth or filter material. (Being careful not to excessively impede breathing.)

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Attribution: Ryssby at English Wikipedia)