Facial hair including mustaches and lower lip hair must not interfere with what?

Facial hair, particularly mustaches and lower lip hair, is required to not interfere with the seal of the facemask because a proper seal is critical for the effectiveness of personal protective equipment, specifically in maintaining respiratory protection. When the facial hair touches or crosses the seal of the facemask, it can create gaps that allow unfiltered air to enter, which can compromise the safety of the individual wearing the mask. This is especially important in firefighting and hazardous environments where toxic smoke and hazardous materials may be present. Maintaining an effective seal ensures that the respiratory protection performs as intended, providing vital safety to the individual in dangerous situations.

Other considerations like being classy, keeping hair trimmed, or adhering to a length restriction may pertain to personal grooming standards, but they do not directly relate to the critical functionality of protective gear in emergency response situations.