Investigation and modeling of surface sorption/desorption behavior of volatile organic compounds for indoor air quality analysis

Volatile organic compound contents of 20 Kuwaiti houses were measured by pu mped sampling versus time and 17 predominant compounds (namely, benzene, to luene, xylene, styrene, trimethylbenzene, butylbenzene, propylbenzene, dich loroethylene, trichloroethane, dichloropropane, dibromomethane, chloroform, tetrachloroethane, tetrachloroethylene, chlorotoluene, dichlorobenzene and fluorobenzene) have been identified. Other related factors, such as the ou tdoor concentrations, the surface areas of the walls and the furnishings, a nd the previously measured air exchange rates were incorporated in a transi ent mass balance model which also took into consideration the phenomenon su rface sorption and the source emission. An integrated form of this model wa s used to analyze the experimental time-averaged concentration data. A plot of indoor concentration versus outdoor concentration for a specific VOC ga ve a straight line from which the removal rate by adsorption and the source emission were obtained. It was found that the data correlated satisfactori ly if the surface area for sorption was estimated based not only on the sur faces of walls, ceiling and floor (an approach often used by other workers in previous studies) but also those of all components of interior, such as those of furniture. me surface sorption rate constants for each VOC under s tudy were evaluated and they varied between 0.2 to 0.96 m hr(-1) depending on the chemical nature of the VOCs. These results showed also that the remo val rates of aliphatic and aromatic VOCs by adsorption increased if they we re attached to halogen and alkyl groups respectively. On the other hand, re latively low removal rates were observed when unsaturated alkyl and phenyl groups were attached to a halogen.