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Thermocouples have been widely used to measure temperature in research and industry. For the purpose of building fire experiments, the thermo couple has been and will be a major instrument to obtain the temperature field of the fire environment, and hence to quantify the intensity of building fire. It has been found that the radiation error significantly affects the measured tempera ture using thermocouples. However, this issue has not been carefully investigated in the area of building fire research.A suction pyrometer was designed and applied to a series of fire experiments in a full-scale experimental building-fire facility to avoid the effect of radiation on the measured temperature. It was found that the reading from a bare thermocou ple could be more than 100°C higher than the gas temperature obtained from the suction pyrometer during the flaming fire stage and more than 200°C higher dur ing the flashover stage.For a steady-state fire environment obtained from a propane gas burner fire, the radiation error was negligible in the hot upper level near the ceiling. However, the thermocouple significantly overestimated the gas temperature by more than 80°C in the cool lower level near the floor because of the radiation error. The tem perature predicted by the computational fluid dynamics model, CESARE-CFD fire model, was in good agreement with the measured temperature after the ra diation correction in the lower level and deviated slightly in the upper level.