The rate of ozone uptake on carpet: mathematical modeling

To better understand the factors that control indoor pollutant concentrations, we developed a model describing mass transport and uptake of reactive gases on carpeting. First, an existing model of particle deposition from turbulent flow to indoor surfaces was extended to include surface resistance to the uptake of reactive gases. This model parameterizes surface resistance in terms of the pollutant–surface reaction probability, γ. We develop an approach for predicting the effective reaction probability of carpet from its geometric parameters and from experimentally measured uptake probabilities of ozone on carpet fibers, γf, and carpet backing, γb. A comparison of predictions with empirical data for several carpet samples shows good agreement, with a typical value of γ 10−5. For this value of γ and for typical turbulent indoor airflow conditions (i.e., friction velocity in the range 0.3–3 cm s−1), the deposition velocity of ozone onto carpet should lie in the range 0.016–0.064 cm s−1, values that are consistent with field measurements. Owing to its higher reaction probability, carpet backing is predicted to consume approximately the same amount of ozone as carpet fibers, even though the available surface area of the fibers is much larger.