Volatile organic compounds (VOCs) are frequent indoor air pollutants. Indoor materials can act as buffers for VOCs, reducing peak concentrations but prolonging the presence of compounds in the air. The purpose of this paper is to present quantitative experimental results on diffusion and sorption of VOCs in indoor materials and to discuss the impact of these processes on indoor air quality. A two-flow system was chosen for the present study because this method allows mass flow across materials to be directly observed. For some materials, effective diffusion coefficients were only 1 order of magnitude below what is found in air. Two types of concrete showed a very high sorption capacity for ethyl acetate. Steady-state calculations were performed within a model room. By considering various wall materials, the influences of diffusion and of sorption on the air quality of the room are discussed. Regarding the case of gypsum board walls, it may be concluded that diffusion through the material can contribute to reducing the room air concentration, especially at low ventilation rates. The results indicate that sorption and diffusion processes can affect the ventilation requirements in such rooms.

The emissions from five commonly used building products were studied in small-scale test chambers over a period of 50 days. The odor intensity was assessed by a sensory panel and the concentrations of selected volatile organic compounds (VOCs) of concern for the indoor air quality were measured. The building products were three floor coverings: PVC, floor varnish on beechwood parquet and nylon carpet on a latex foam backing; an acrylic sealant, and a waterborne wall paint on gypsum board. The impacts of the VOC concentration in the air and the air velocity over the building products on the odor intensity and on the emission rate of VOCs were studied. The emission from each building product was studied under two or three different area-specific ventilation rates, i.e. different ratios of ventilation rate of the test chamber and building product area in the test chamber. The air velocity over the building product samples was adjusted to different levels between 0.1 and 0.3 m s\. The origin of the emitted VOCs was assessed in order to distinguish between primary and secondary emissions. The results show that it is reasonable after an initial period of up to 14 days to consider the emission rate of VOCs of primary origin from most building products as being independent of the concentration and of the air velocity. However, if the building product surface is sensitive to oxidative degradation, increased air velocity may result in increased secondary emissions. The odor intensity of the emissions from the building products only decayed modestly over time. Consequently, it is recommended to use building products which have a low impact on the perceived air quality from the moment they are applied. The odor indices (i.e. concentration divided by odor threshold) of primary VOCs decayed markedly faster than the corresponding odor intensities. This indicates that the secondary emissions rather than the primary emissions, are likely to affect the perceived air quality in the long run. Some of the building products continued to affect the perceived air quality despite the concentrations of the selected VOCs resulted in odor indices less than 0.1. Therefore, odor indices less than 0.1 as an accept criterion cannot guarantee that a building product has no impact on the perceived air quality.

No abstract

No abstract

No abstract