Active underground areas that cannot be supplied through natural/mechanical ventilation require an airline with how many air valves at the entrance and the end of the pipe?

Active underground areas that cannot be supplied through natural/mechanical ventilation require an airline with how many air valves at the entrance and the end of the pipe?

• A. 2
• B. 1
• C. 3
• D. 4

Answer: (A)

When you must ventilate an active underground area that can’t be reached by natural or existing mechanical ventilation, you supply air through an airline. To safely control and isolate that supply, you need two air valves—one at the entrance of the pipe and one at the far end. Having a valve at the entrance lets you start or stop the air supply from the surface and helps protect the main ventilation flow by allowing quick isolation of the airline if needed. The valve at the far end enables you to shut off flow to the far section, prevent backflow if there’s a leak, and facilitate purging, testing, or maintenance of the line. With both ends valved, you can securely manage the entire length of the airline and ensure the downstream area receives clean air without unintended leakage or crossflow.

When you must ventilate an active underground area that can’t be reached by natural or existing mechanical ventilation, you supply air through an airline. To safely control and isolate that supply, you need two air valves—one at the entrance of the pipe and one at the far end.

Having a valve at the entrance lets you start or stop the air supply from the surface and helps protect the main ventilation flow by allowing quick isolation of the airline if needed. The valve at the far end enables you to shut off flow to the far section, prevent backflow if there’s a leak, and facilitate purging, testing, or maintenance of the line. With both ends valved, you can securely manage the entire length of the airline and ensure the downstream area receives clean air without unintended leakage or crossflow.