If you want a respirator to provide its full protective benefits and work properly, it cannot be worn with a beard or facial hair. Disposable and reusable respirators must seal tightly to the face so that air entering the facepiece is forced through the filter or cartridge, thereby filtering airborne hazards from the air. If the seal to the face is not secure, air will go around the face seal rather than through the filter, as it takes the path of least resistance. That is why it is essential to ensure a proper seal when wearing a respirator. Facial hair such as beards, sideburns, or some mustaches can interfere with the seal of the respirator by creating gaps in the seal. These gaps allow air to leak into the respirator, reducing protection. A short mustache or goatee may be acceptable, but it must fit completely inside of the respirator.