What is the minimum number of automatic methane detectors required to monitor the ventilating air passing through the main exhausting fan?

• A. One detector minimum
• B. Two detectors minimum
• C. Three detectors minimum
• D. Four detectors minimum

Answer: (A)

The essential idea is to monitor the air where it matters most for detecting methane before it poses a risk as the mine air is discharged. For the main exhausting fan, placing an automatic methane detector in the ventilating air that passes through that fan provides direct, continuous monitoring of the air leaving the mine. This single detector can trigger alarms and ventilation responses if methane rises, giving the necessary protection with the simplest, minimal setup. While additional detectors could be added for redundancy or broader coverage, the question asks for the minimum number required for the main exhaust air path, which is one.