title: Diffusion-controlled reference material for VOC emissions testing: effect of temperature and humidity.
abstract: A polymethylpentene film loaded with toluene is being developed as a reference material to support the reliable measurement of volatile organic compound emissions from building materials using environmental chambers. Earlier studies included the measurement of the material-phase diffusion coefficient (D) and material/air partition coefficient (K) at 23°C. A fundamental mass-transfer model can then be used to predict toluene emissions from the reference material at 23°C, serving as a reference for validating chamber-measured emission profiles. In this study, the effect of temperature and humidity on performance of the reference material was investigated. Reference material emissions were measured at 10, 23, and 30°C and at different relative humidity (RH) levels. D and K at different temperatures and RH were determined using an independent method. Results showed that RH does not significantly affect D and K and had no effect on emissions. However, emissions increased substantially at elevated temperatures due to the relationship between D and temperature. A statistical analysis shows good agreement between model-predicted and measured gas-phase concentrations, indicating that the model can accurately predict emission profiles as a function of temperature. The reference material can therefore be applied to a wide range of emission chamber testing conditions.
  
  
  CONCLUSIONS
  A reference material with a dynamic emissions profile was previously developed as a validation tool for emission testing in chambers. This follow-up study investigated the effect of temperature and humidity on the performance of the reference material. The results show that the reference material can be used to calibrate and validate chamber testing procedures over a broad range of environmental conditions.
authors.affiliation: Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
authors.forename: C
authors.initials: C
authors.lastname: Howard-Reed
authors.forename: S S
authors.initials: SS
authors.lastname: Cox
authors.forename: W
authors.initials: W
authors.lastname: Ye
authors.forename: J C
authors.initials: JC
authors.lastname: Little
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis*; D004058:Diffusion; D006813:Humidity; D008962:Models, Theoretical; D011090:Polyenes / Q000737:chemistry*; D013696:Temperature; D014050:Toluene / Q000032:analysis*
chemical_list: D011090:Polyenes; D014050:Toluene; C021245:poly(methylpentene)
keywords: Chamber; Desorption; Indoor; Model; Sorption; Validation