Human exposure chamber for known formaldehyde levels:: Generation and validation

Formaldehyde is a common air pollutant of the indoor environment. It has a potential effect on the respiratory function of people and so studies have been performed to assess this using exposure methods with high concentrations of formaldehyde. However, epidemiology studies have shown its impact on allergic diseases at lower domestic levels. The aim of this study was to develop an exposure chamber to study effects of low controlled concentrations of formaldehyde. Concentrations in the chamber were quantified by a simple DNHP-derivatisation method followed by liquid chromatography coupled to UV detection. Experiments to assess formaldehyde generation yield and reproducibility of formaldehyde levels in the chamber were performed in an empty chamber. The temporal decay of formaldehyde concentration in the exposure chamber was also investigated for more than 2 h under different experimental conditions, for example in darkness or with somebody inside the chamber. Actual measured levels of formaldehyde were found to be 78-91% of the calculated value expected. The study of the temporal decay showed that subject's breathing accounted for the fate of approximately 50% of the formaldehyde lost. Leaks, wall deposition, photolysis and adsorption on clothes were processes identified to explain the remaining 50%. However, this study has shown that both homogeneity and stability of formaldehyde concentration in the gas phase can be maintained acceptably to carry out future human exposure experiments.