What is the maximum number of negative air exhausts that can be discharged at the same termination point?

• A. 3
• B. 5
• C. 7
• D. 10

Answer: (B)

In asbestos work, keeping fibers from spreading relies on maintaining negative pressure in the work area while exhausting air outside. When several negative air exhausts are all discharged at the same exterior termination point, the flow at that point becomes a point of control for multiple air streams. Limiting how many exhausts can join there helps prevent backflow, cross-flow between machines, and loss of containment if one unit changes speed or its damper is misadjusted. Five is the practical limit that balances having enough exhaust capacity for multiple machines with keeping the exterior discharge manageable and predictable. If more exhausts are needed, use additional termination points or properly designed separate exhaust routes, and verify the system’s negative pressure and containment with appropriate monitoring.