To improve the reliability and accuracy of chamber tests for measuring emissions of volatile organic compounds (VOCs) from interior materials, Virginia Tech (VT) and the National Institute of Standards and Technology (NIST) have created a program to develop reference materials for VOC emissions testing. A prototype reference material has been developed by loading toluene into a polymethylpentene (PMP) film. Its emission characteristic parameters, including material-phase diffusion coefficient (D) and material/air partition coefficient (K), have been measured at 23 ºC. A fundamental mass-transfer model can then be used to predict the true toluene emission rate from the reference material at 23 ºC, which serves as the reference value for validating the results measured by different laboratories. In this paper, the impact of temperature and humidity on the performance of the reference material was investigated. Emissions from the reference material were measured in chambers at 10, 23 and 30 ºC and at different relative humidity (RH) levels. D and K values at different temperature and RH levels were also determined using a completely independent microbalance method. It was found that RH level does not significantly affect D and K and has no impact on emission chamber test results. However, D and K depend strongly on temperature and emissions are enhanced substantially at elevated temperatures. At all the test temperatures, the model predictions match the chamber test results very well, suggesting that it can indeed predict the true emission rates at different temperatures. The reference material can therefore be applied to a wider range of emission chamber testing conditions.
Citation: Indoor Air
Pub Type: Journals
diffusion, emissions, humidity, reference materials, temperature, volatile organic compounds