Where must the visual alarm be visible when the automatic methane detector in an intake airway detects high concentrations of methane?

The correct choice pertains to the critical need for safety measures in mining environments, particularly when managing the risks associated with methane exposure. The visual alarm must be positioned at the interface between a non-explosive risk zone and an explosive risk zone because this location is pivotal for immediate awareness and response.

When an automatic methane detector triggers due to elevated methane levels, it is essential for personnel to be alerted right where the safe area transitions to a hazardous one. This placement of the visual alarm ensures that workers can quickly recognize the impending danger and take appropriate safety measures, such as moving to a safer location or initiating emergency protocols.

This strategic positioning also facilitates effective communication of risk levels to those working in proximity to potentially explosive environments, thus enhancing overall workplace safety. The focus on the interface directly correlates to mitigating risks associated with methane, which is crucial in mining operations where explosive mixtures can form.

Other locations proposed for the alarm, such as in the control room or at exits, do not provide the immediate and actionable alert required in a dynamic and potentially dangerous situation where workers might be moving toward hazardous areas.