Robust Nonfitting Way To Determine Mass Diffusivity and Initial Concentration for VOCs in Building Materials with Accuracy Estimation

Abstract

This paper presents a novel procedure for estimating mass diffusivity and initial concentration for VOCs in building materials. In contrast to methods that fit data to an organic emission model, this new method determines these two parameters by two observations from a chamber test in a nonfitting and sequential way, which defines a well-posed problem and requires no iterative procedure as well as is robust to initial guess and random uncertainties. The most outstanding feature of this method is that multiple estimates of the parameters can be obtained when more than two experimental data are available; thus, these estimates constitute a sample of population of parameter estimates involving experimental errors. The averages of the sample can be regarded the best estimates of the parameters, and, more importantly, variances (standard deviations) and confidence intervals can be readily and naturally estimated making no assumption about the distribution of experimental errors. Two easy and direct ways are suggested for determining confidence limits: one is percentile method, and the other is the normal approximation. This feature highlights the major difference between the new method and common curve-fitting procedures that generally assume random errors being Gaussian distribution.

Impact of Temperature on the Ratio of Initial Emittable Concentration to Total Concentration for Formaldehyde in Building Materials: Theoretical Correlation and Validation

“…Three emission characteristic parameters, the initial emittable concentration ( C m,0 ), the diffusion coefficient ( D m ), and the partition coefficient ( K ), are found to be useful for describing formaldehyde and VOC emissions from building materials. − It should be noted that these three emission parameters are dependent on the physical properties of the material–pollutant combinations as well as environmental conditions (e.g., temperature, relative humidity). At present, methods to measure C m,0 , D m , and K are well developed under certain conditions.…”

Indoor air formaldehyde (HCHO) pollution of urban coach cabins

“…For example, except time, the HCHO steady state can be influenced by other factors including indoor temperature, relative humidity, solar radiation and cabin ventilation, and these factors may simultaneously affect the HCHO emission, which make that the physical mechanism analysis of HCHO emission is complex 20 . Moreover, the HCHO emission process of indoor materials is characterized by three key parameters including diffusion coefficient (DC), partition coefficient (PC) and initial emission concentration (IEC) [26][27][28][29][30] . For a certain value of the IEC or DC, the relative sensitivity coefficient decays rapidly over time and tends to a small value when the emission time is long enough 26 .…”