The authors evaluated the free formaldehyde concentration at different sections of a MDF production line with capacity of 200 000 m3/a,with special attention in the area around the forming machine and hot-press.The results showed that the formaldehyde concentration was less than 0.12mg/m3 in the control room and defibrator workroom which means it can meet the standard requirements.The formaldehyde concentration in the store house was 0.16 mg/m3,thus requiring ventilation.The formaldehyde concentration in the forming and hot-pressing areas was 0.33mg/m3 and 0.86 mg/m3,respectively,requiring measures to improve the ventilation or to add worker safety facilities.