Multigas detectors detect Oxygen, CO, LEL, and?

Multigas detectors detect Oxygen, CO, LEL, and?

• A. Methane
• B. Hydrogen sulfide
• C. Ammonia
• D. Nitrogen dioxide

Answer: (B)

The key idea is what a standard four‑gas detector is built to monitor in many firefighting and rescue environments. It normally tracks oxygen levels, carbon monoxide, and a reading for explosivity of flammable gases (the LEL). The fourth sensor is hydrogen sulfide because H2S is a common toxic gas in confined spaces and industrial settings, and it requires its own sensor due to its high toxicity at low concentrations. Methane would already be covered by the LEL reading, and ammonia or nitrogen dioxide are not the typical fourth gas in the standard four‑gas setup. So the best answer is hydrogen sulfide.

The key idea is what a standard four‑gas detector is built to monitor in many firefighting and rescue environments. It normally tracks oxygen levels, carbon monoxide, and a reading for explosivity of flammable gases (the LEL). The fourth sensor is hydrogen sulfide because H2S is a common toxic gas in confined spaces and industrial settings, and it requires its own sensor due to its high toxicity at low concentrations. Methane would already be covered by the LEL reading, and ammonia or nitrogen dioxide are not the typical fourth gas in the standard four‑gas setup. So the best answer is hydrogen sulfide.