What is the multi-gas detector's low alarm level for methane?

• A. 1% or below
• B. 2% or below
• C. 0.5% or below
• D. 5% or below

Answer: (A)

Think about how alarms protect you from gas before it becomes dangerous. For methane, the low alarm on a multi-gas detector is set to warn at around 1% by volume in the air. This gives you early notice long before the gas could reach a level that’s dangerous or explosive (the explosive limit for methane is about 5% in air), so you have time to increase ventilation, evacuate if needed, or take other safety actions. Setting the alarm at 1% balances prompt warning with avoiding constant nuisance alarms that would happen with a much lower threshold. If the alarm were higher, you’d get warned later, which isn’t as protective; if it were much lower, you’d have frequent alarms during normal operations.