Final answer:
The SEED should not be worn for fire-fighting purposes. A SCBA is the most suitable breathing device for firefighters.
Step-by-step explanation:
The breathing device that should NOT be worn for fire-fighting purposes is the SEED.
A Self-Contained Breathing Apparatus (SCBA) and an Open-Circuit Breathing Apparatus (OBA) are both used by firefighters for respiratory protection in fire-fighting situations. However, a SCBA is the most suitable breathing device as it provides the highest level of protection with a full face mask, regulator, and a supply of clean air from a compressed air cylinder.