According to OSHA, you can wear a respirator with facial hair when the hair doesn't get in the way of the sealing surface or interfere with the valve function. If you have sideburns, a mustache, or a goatee, always ensure it is well-trimmed to prevent it from protruding under the seal. Some respirators are designed for people with a beard. You can consider getting one as this way you will be assured there's no leakage and you're well protected even with facial hair.