What is one requirement for the o-ring inside the coupling nut?

The requirement for the o-ring inside the coupling nut to be free of damage is essential for ensuring the integrity and safety of the SCBA system. A damaged o-ring can lead to leaks, which would compromise the respiratory protection provided by the apparatus. Proper seals are critical in maintaining the pressure of the air supply and preventing contamination from outside air. Hence, ensuring that the o-ring is intact and undamaged is vital for the reliable operation of the SCBA, thereby upholding the safety of the user in hazardous environments.