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Developing a Reference Material for Formaldehyde Emissions Testing; Final Report
Citation:
Little, J., Z. Liu, X. Zhao, AND S. Cox. Developing a Reference Material for Formaldehyde Emissions Testing; Final Report. US Environmental Protection Agency, Cincinnati, OH, EPA/600/R/13/001, 2013.
Impact/Purpose:
This research is to develop a formaldehyde reference material to be used for identifying and eliminating or minimizing the root causes of formaldehyde emissions measurement variability in the test chambers.
Description:
Exposure to formaldehyde has been shown to produce broad and potentially severe adverse human health effects. With ubiquitous formaldehyde sources in the indoor environment, formaldehyde concentrations in indoor air are usually higher than outdoors, ranging from 10 to 4000 μg/m3. As a result, industry and government are taking actions to minimize formaldehyde exposure in the indoor environment. A critical step toward mitigating formaldehyde exposure in the indoor environment is assessing the potential of building materials and indoor furnishings to emit formaldehyde. These assessments usually involve emissions measurements obtained using environmental chambers. However, some variability currently exists with respect to chamber testing results. A formaldehyde emissions reference material could be used to identify and eliminate or minimize the root causes of formaldehyde emissions measurement variability. The objective of this research project was to create and evaluate such a reference material.The formaldehyde emissions reference material development progressed through the following major steps: (1) identifying a suitable polymer film for use as a reference material and characterizing its mass-transfer properties; (2) loading formaldehyde into the selected polymer film; (3) predicting formaldehyde emissions from the pre-loaded polymer films through the use of a fundamental emission model; and, (4) measuring formaldehyde emissions from the pre-loaded films in small-scale environmental chambers. The reference material was evaluated by (1) comparing actual formaldehyde emission profiles measured using small-scale emission chambers to model predictions; (2) ) evaluating the effect of storage duration; (3) evaluating the effect of the packaging material; and, (4) investigating how reference material formaldehyde emissions were affected by humidity.Polycarbonate film was selected as a suitable reference material substrate due to its relatively large partition coefficient with respect to formaldehyde. Using measured mass transfer coefficients and chamber parameters, the emissions model was used to predict formaldehyde concentration profiles during small-scale chamber testing. Although measured chamber concentrations tended to be lower than model predictions in early time periods and higher than model predictions in later time periods, the measured emission profiles were overall quite similar to model predictions.Subsequent chamber tests were conducted to evaluate the effect of reference material storage duration. Results suggested that some formaldehyde was lost from the reference materials over time but also showed good agreement with model predictions over the course of 144-hour tests when samples had been kept in storage for periods of less than 2 weeks.The lasttwo evaluations included testing the effect of the foil packaging material and the effect of humidity on formaldehyde emissions. Results of the packaging material test indicate that a tight aluminum foil wrap reduces but does not eliminate formaldehyde loss from the reference material. Although the results of the humidity evaluation were not entirely consistent, the data suggests that formaldehyde emissions from the reference material are affected by humidity. This could be due to water molecules plasticizing the polymer film or perhaps causing depolymerization of formaldehyde on the surface of the reference material.