A diffusive sampling device was developed for screening indoor sources of formaldehyde and determining the emission rates of these sources on-site. It consists of a glass Petri dish containing a quartz filter coated with 2,4-dinitrophenylhydrazine (DNPH) which is placed on the tested material for sampling. Formaldehyde emitted from the material diffuses through the air column inside the sampler and is collected onto the DNPH filter. The formaldehyde emission rate is determined from the mass collected by the sampler. The dependence of the sampled formaldehyde amount on the diffusion length inside the sampler was examined and led us to select a length of 20 mm for which the diffusion in the air layer controls the mass transfer from the material to the sampling surface (filter). A linear relationship with a high correlation (r2 = 0.97) was obtained between the mass collected by the passive flux sampler and the emission rates measured by a standard chamber method, analysing a large series of indoor materials with the two methods in parallel. Neither the sampling time (ranging from 4 to 8 h) nor the temperature (from 23 to 35 °C) was observed to influence the sampler performance. Furthermore, the detection limit attained 1.2 μg m−2 h−1 for a 6h-sampling time and a satisfying precision of replicate measurements (relative standard deviation of 7.8% on average) is adequate for monitoring the emission rates of primary sources contributing to formaldehyde indoor concentrations.
