The effects of the selective addition of the gases H2, CO, O2, NO, NO2, and N2O on the output peak power and stability of a flowing-gas TEA laser operating with a basic mixture of CO2, N2, and He are examined. These additive gases are possible products of reactions which occur in the discharge region of the laser and have considerable bearing on the operation of a sealed TEA laser. The power output is increased with the limited addition of H2 (~5 percent) or NO (~0.2 percent), whereas N2O, NO2, O2, and CO reduce the power output when present in any amount; 50-percent reduction being obtained with ~0.23-percent N2O, ~0.15-percent NO2, ~4-percent O2, and ~22-percent CO. H2 (and possible NO) limits the transition from a diffuse glow to arc discharge by allowing a larger range of operating conditions, whereas CO reduces the range of operating conditions for stable operation. O2 does not affect the discharge, whereas N2O and NO2 both encourage the transition to arcing. Copyright š 1975 by The Institute of Electrical and Electronics Engineers, Inc.