Final answer:
Soot can reduce visibility on the facepiece of a protective breathing apparatus.
Step-by-step explanation:
Soot can reduce visibility on the facepiece of a protective breathing apparatus. The facepiece is the part of the apparatus that covers the wearer's face and provides a seal to prevent the inhalation of smoke or other harmful substances. When soot accumulates on the facepiece, it can obstruct the wearer's vision and make it difficult to see, potentially compromising their safety.