The reliability of models for converting formaldehyde emissions from wood-based materials to different environmental conditions

Abstract

The monitoring of the formaldehyde emission potential of wood-based materials by means of test chamber investigations has been established by national and international standards and has made an important contribution to significantly reducing the formaldehyde concentrations indoors. The procedures used are mostly methodologically different, so that the results cannot be directly compared. The first empirical models for converting formaldehyde steady-state concentrations as a function of temperature, air humidity, air change rate and loading were derived in the 1970s. However, the development of lower-emitting materials made it necessary to modify and adapt these models. Formaldehyde emissions from wood-based materials are complex from both a reaction-kinetic and dynamic perspective. There is an exponential dependence of the steady-state concentration on temperature and humidity and an inverse proportionality to the air change rate. The mathematical analysis requires multiple non-linear regression tools. A large data set with reliable results obtained under different conditions is available from previous investigations. With a total of 128 measurement data, there was very good agreement between theory and experiment for a wide range of chamber settings from a statistical point of view. However, the model is not suitable for predicting the emission behavior of individual products. Some uncertainty also exists due to the allowed tolerance limits of the chamber parameters. Since the formaldehyde emission rate depends on the air change rate, a simple linear conversion of steady-state chamber concentrations into room air concentrations for indoor exposure assessments is not possible even at constant temperature and humidity.