From where can supplied air be sourced?

Supplied air should come from an uncontaminated environment to ensure that the air is free from harmful substances and pollutants. This is crucial for the safety and health of workers, especially in environments where they may be exposed to hazardous materials like asbestos. When air is sourced from an uncontaminated environment, it is generally processed and filtered to meet safety guidelines, providing a clean and breathable air supply.

The other options present limitations or risks. For instance, sourcing air from contaminated tanks or chemical plants can introduce harmful toxins and respiratory hazards, undermining the purpose of using supplied air. Sealed containers might not provide a sustainable or adequate air supply and may not ensure the required air quality, especially if there are unknown contaminants. Thus, relying on an uncontaminated environment is essential for maintaining a safe working atmosphere.