A long term field study was conducted in an office to clarify the effect of thermal environment on productivity. The field study was conducted from July 4, 2005 to January 18, 2006. During the field study the office was cooled by air-conditioner. Under low temperature condition, the percentage of dissatisfied was increased, the total number of typing of one day and the reaction rate of Advanced Trail Marking Test (ATMT) was decreased. There was a decrement of the total number of typing of one day in 6.3% when temperatures dropped by 1℃ below 28.6℃. Too much cooling conditions might bring the decrement of performance in the office.
