Final answer:
The source used to refill an SCBA must provide clean air.
Step-by-step explanation:
The source used to refill a Self-Contained Breathing Apparatus (SCBA) must provide clean air. SCBA is a type of respiratory protective equipment used by firefighters and other emergency responders to protect against smoke, fumes, and hazardous gases in the atmosphere. The air quality inside an SCBA tank should be free from any contaminants or toxins that could pose a health risk to the user.