Repeatedly brief releases of contaminants may for example be due to different types of indoor activities. The binding of contaminants by building materials may at first sight be seen as an advantage. The depot-effect initially decreases the concentration in air. The secondary emission, however, continues over a long period of time and may lead to an increased accumulated exposure dose for anyone in the indoor environment.
Although the existence of these effects has long been known there has been a lack of sufficient physical-chemical data on the interaction between different compounds and materials. Researchers have therefore been unable to draw any certain conclusions as to the importance of these effects for indoor air quality and the corresponding health consequences. The goal of this project is both to develop such a mathematical model, which allows description of the interaction in a satisfactory way, and to determine material parameters, needed for the model. From this, conclusions can be drawn on the importance of the depot-effect on indoor air quality and subsequently also on the risk involved in using various consumer chemicals in relation to the effects of primary emissions from building and other indoor materials - a matter which is considerably more thoroughly investigated.
The depot effect has been studied experimentally using a dynamical method in a small exposure chamber where the test material is exposed for contaminated air at a given temperature, humidity and velocity. However, additional experiments are planned in the present project, in order to improve the understanding and modeling:
Much emphasis has been placed on the development of a mathematical model, based on fundamental physical processes, to interpret the experimental results. This model is the basis for quantifying the adsorption/desorption process in the real environment. The depot models will therefore be coupled with compartment and fluid dynamics models (CFD) for ventilated environments in the present project.
The development of models will be made with support from experiments in a new medium sized climate chamber which is planned to be constructed within the project. Lastly, validation of experiments will be performed in full-scale experimental rooms in the laboratory.