Breathing tubes; minimum requirements.

Flexible breathing tubes used in conjunction with supplied-air respirators shall be designed and constructed to prevent: (a) Restriction of free head movement; (b) Disturbance of the fit of facepieces, mouthpieces, hoods, or helmets; (c) Interference with the wearer's activities; and (d) Shutoff of airflow due to kinking, or from chin or arm pressure.