A test method is described and experimental data are presented which compare formaldehyde emissions from edges and surfaces of particleboards. Surface emissions from boards of different structures and resins are also presented. Porosity of particleboards was measured and related to formaldehyde emission. It was found that porosity of the board is a major controlling factor in formaldehyde emission. It appears that the rate of formaldehyde release from particleboards is a diffusion controlled process.