tunnel ventilation

[do032594]

The project Im working on is to provide a second means of exit/egress to an existing coal pile reclaim conveyor which is about 25 feet below grade. There is currently one exit/egress so I will provide a second tunnel to the tail end of the conveyor below grade. I will also provide an exhaust fan at one of the exit/egress to pull outside fresh air through both the existing tunnel and the tunnel at the tail of the conveyor. My question is there a standard out there that would help me design the system? NIOSH, OSHA, NFPA, Does the outside air coming in need to be filtered before it comes in?, ...before it goes out? How many CFM? anything else?

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