During full-scale fire suppression tests using HFC-227ea and HCFC Blend A, the Fourier transform infrared spectroscopic method was used to monitor the gas composition of the air in a 121 m3 test compartment. These agents were observed to produce halogenated compounds during the tests. The production of the halogenated gas compounds depended on the type and concentration of the agents and on the size and extinguishment time of the test fires. Quantitative analysis of infrared spectra indicated that the concentrations of the halogenated compounds were at dangerous levels during suppression. Safety measures should be taken to prevent persons from being exposed to these toxic gas compounds and to minimize potential corrosion damage to equipment.