From component testing to system prediction of VOC emissions from office furniture

One approach of estimating volatile organic compound (or VOC) emissions from furniture is component-to-system prediction, i.e., to predict VOC emissions from a furniture system using data from tests of the components and/or materials of the system. This study examines the validity of component-to-system prediction. Typical workstation systems were tested in a full-scale chamber while the components of identical workstation systems were tested in a mid-scale chamber and the material specimens were tested in small-scale chambers. Wood structure chairs were tested in mid-scale chamber while their components and materials were tested in small-scale chambers. The power-law model (i.e., E = a t^-b, where, E is the emission factor in μg/h per emission unit; t is time in h, and a, b are empirical coefficients determined from chamber test data) was used to describe the VOC emission rates. A multilayer diffusion model was developed to help understand the behavior of VOC emissions from multilayer structures, and to evaluate the limitations of the power-law model. Theoretical analysis and experimental results are used for the investigation. Two of the factors that affect the validity of component-to-system prediction of VOC emissions from furniture are examined: (1) back pressure effect, and (2) time delay effect. The back pressure in this context refers to the vapor pressure of gas phase VOC in the surrounding air of the test furniture. An analysis shows that, the VOC emissions from a system can be predicted within the experimental error for selected VOCs of interest if the tests of the components are conducted with the same L/ACH (or A/Q) ratio (i.e., ratio of loading ratio, L, to air change rates per hour, ACH), and the effect of time delay in testing is taken into account.