The formaldehyde release from particleboard under changing climatic conditions and with varying amounts of exposed particleboard was studied in a large climate chamber. A mathematical model was developed which describes the influence of the various parameters on the formaldehyde concentration in the atmosphere of a room containing particleboards. After determining the formaldehyde concentration under standard conditions by a laboratory method, the formaldehyde concentration under any other climatic conditions can be calculated. The mathematical relations presented in this article are of model character, therefore, they cannot be transferred uncritically to every board system.