Characteristics of formaldehyde emissions from indoor materials assessed by a method using passive flux sampler measurements

•An original method to characterize the air boundary layer on the surface of materials.•Assessment the thickness and concentrations of the boundary layer on some materials.•Study on the representativeness of such data for materials in real indoor conditions.

A method was developed and tested to characterize the gas-phase boundary layer developing on the surface of seven indoor materials from formaldehyde emission measurements carried out under environmental chamber conditions using passive flux samplers having different diffusion lengths. This indirect approach consistently provides many assessed values of gas-phase boundary layer thickness with a mean and range of 31.6 ± 17.4 mm. These experiments also yield other information like the gas concentration on the material surface as well as the concentration gradient inside the gas-phase boundary layer. Linear relationships were found between formaldehyde gas concentration on the material surface, the concentration gradient inside the gas-phase boundary layer and the emission rate. Data and relationships should be useful for parameterizing and modeling formaldehyde emissions from indoor surfaces.