This technical note considers the performance evaluation of an advanced air-conditioningsystem in a plant manufacturing electrical generators. The extensive field measurements ofthermal climate and indoor air quality were performed during five periods of extreme weatherconditions in 1994-1996. In order to describe the performance of the air-conditioning system,the thermal climate and indoor air quality were determined. The air-conditioning system wasable to maintain the thermal climate within the range recommended in the ISO standard 7730for most of the time. The total volatile organic compound (TVOC) concentration wasnormally 0.6 mg/m, close to the levels typically found in non-industrial environments. Apartfrom the summer of 94 and the winter of 95 the dust concentrations were slightly higher thanthose in offices. In conclusion, it seems that the thermal climate and indoor air quality inproduction rooms with advanced air-conditioning system is approaching to that of offices.