What is the primary use of a transmissometer in opacity monitoring?

The primary use of a transmissometer in opacity monitoring is indeed to assess particulate matter. A transmissometer operates by measuring the amount of light that passes through a sample of air or a gas. When particulate matter such as smoke, dust, or other particles is present, it will scatter and absorb some of the light.

By analyzing the reduction in light intensity, the transmissometer can quantify the opacity of the medium. Opacity refers to how opaque a mixture is, which directly correlates to the concentration of particulate matter present. Therefore, the device provides critical information about air quality and emissions from combustion sources or industrial processes, helping to ensure compliance with environmental regulations and to assess the performance of filtration systems.

The other choices do not align with the function of a transmissometer. Sound level measurements are related to acoustics, while temperature regulation and light intensity alone do not directly pertain to opacity monitoring in the context of particulate assessment. Thus, the focus on assessing particulate matter is what makes this particular application of the transmissometer significant.