What is the minimum detector placement requirement for ERZ0 and ERZ1 in a longwall return airway?

• A. Detectors must be in ERZ0 only
• B. Detectors must be in ERZ1 only
• C. Detectors must be in ERZ0 and ERZ1 if a machine can cross boundaries
• D. Detectors are not required

Answer: (C)

In this context, you’re testing how gas detection coverage must work when a machine can move across boundaries between ERZ0 and ERZ1. If the longwall equipment can cross from one ERZ into the other, a single detector location won’t reliably catch gas that may be present in the other zone. You need detectors in both ERZ0 and ERZ1 so that any gas accumulation or release is detected no matter where the machine is. That enables timely ventilation adjustments or shutdown actions to protect occupants and maintain air quality.

Detectors in only one ERZ would miss gas in the other, and having no detectors at all would ignore potential hazards, so those options don’t meet safety requirements.