Which four gases does the M40M monitor?

The M40M monitor is designed to detect specific gases that are commonly associated with hazardous environments, particularly in industries such as mining and oil and gas. The correct answer identifies the four gases that this monitor can accurately measure: oxygen (O2), methane (CH4), carbon monoxide (CO), and hydrogen sulfide (H2S).

Understanding the significance of each of these gases highlights why this answer is correct. Oxygen is critical for combustion and respiration; therefore, monitoring its levels is essential to ensure safety. Methane is a common combustible gas that can lead to explosions in confined spaces. Carbon monoxide is a toxic gas produced from incomplete combustion and poses serious health risks. Hydrogen sulfide, known for its characteristic rotten egg smell, is also highly toxic and can be lethal in high concentrations.

The other options include gases that are either not typically monitored by the M40M or are not relevant to the primary concerns of this device. For example, nitrogen (N2) and ammonia (NH3) are not primary focus gas types for the M40M monitor, which is specifically tailored for detecting gases that pose immediate risks to health and safety in various industrial applications.