The minimum grade of air for a Type C supplied air system is:

• A. Grade A
• B. Grade B
• C. Grade G
• D. Grade F

Answer: (C)

Air quality for Type C supplied-air systems must meet a predefined breathing-air grade because the wearer relies on an external air source rather than filtering air at the facepiece. The air has to be clean and dry, with limits on oils, moisture, particulates, and certain contaminants so breathing it doesn’t introduce new hazards during asbestos work. Grade G is the minimum grade that provides this level of purity for a Type C system, giving adequate protection while keeping the supply practical and cost-effective. Using air below Grade G wouldn’t guarantee sufficient purity, while higher grades exist for stricter situations; Grade G serves as the baseline requirement for this setup.