The decay of a pollutant in indoor air quality modeling is assumed to follow which type of degradation?

In indoor air quality modeling, the decay of a pollutant is generally assumed to follow first-order degradation. This assumption arises from the idea that the rate of decay of a pollutant concentration is proportional to the current concentration of that pollutant. In practical terms, as the concentration decreases over time, the rate of decay also decreases, aligning with the first-order kinetics model.

First-order reactions are characterized by a linear relationship when the natural logarithm of the concentration is graphed against time; this results in a straight line with a negative slope. This behavior reflects how pollutants usually dissipate in confined spaces due to processes such as ventilation, adsorption onto surfaces, or chemical reactions.

Thus, modeling pollutant decay as a first-order process effectively captures the dynamics of how concentrations change over time in response to removal mechanisms like air exchange or surface deposition, making it a commonly accepted approach in environmental engineering contexts. This understanding is crucial for accurately assessing indoor air quality and determining appropriate measures for pollutant control and ventilation design.