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.

Volatile organic compound (VOC) adsorption by indoor materials will reduce peak concentrations, and subsequent desorption will prolong the presence of a compound indoors. Diffusion within materials plays an important role in this context. The purpose of this paper is to present two experimental set-ups to study VOC diffusion, and to show corresponding experimental results. The Field and Laboratory Emission Cell (FLEC) is in both cases an integral part of the set-up. The mass flow of VOC mixtures across gypsum board is studied. Diffusion of less polar VOCs in gypsum board can be fast (diffusion coefficients of 0.001-0.003 m2/h). Diffusion coefficients of chlorinated compounds are correlated with boiling points and molecular areas. Different compounds show similar diffusion properties.

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Exposure to airborne pollutants can result in adverse health effects. Acute symptoms can for instance comprise of irritation of the eyes or of the respiratory tract (called sensory irritation). In a recent case, health problems were reported in a French school and supposedly attributed to the presence of airborne irritant pollutants. Based on measured concentrations, the risk of developing the described health effects was assessed.Numerous airborne sensory irritants (aldehydes, organic acids, VOCs, SO 2 , NH 3 ) were identified and quantified in the indoor air by using active and passive sampling and online monitoring techniques. Reference values based on toxicological properties of compounds (sensory irritants) were taken from the literature. If not available, tentative values were specially developed for this purpose. Concentrations of all sensory irritants remain below their corresponding guideline values and are comparable to literature data. It was concluded that the risk of developing sensory irritation due to the presence of the studied compounds is negligible. This holds both for individual compounds and for the mixture of studied compounds. Limitations of the employed sampling strategy, and of existing sampling and analytical techniques, which do not allow for analysing more reactive compounds -which are strong sensory irritants -may play a role. New sampling techniques need to be developed. Psychosocial factors (group behaviour, increased attention to sensory irritation) should also be taken into account when dealing with health complaints on sensory irritation.