Present study deals with experimental and theoretical performance analysis of an inert gas generator(IGG) which can be used as an effective mean to suppress the fire. The system consists of a gas turbine engine and afterburning system with injection of water, exit nozzle to produce the inert gas. It is generally known that the degree of oxygen content in the product of combustion depends on both inlet and outlet temperature of a combustor. Less the oxygen content in the combustion product higher will be the effectiveness of fire suppression. Injection of water brings additional advantages of suffocating and cooling effects which are both indespensable factors for fire suppressing. The special test rig was manufactured and experimental investigation of IGG system has been carried out. The automatic control system ensured stable operation of gas turbine engine and afterburner, water injection, fuel control and others. During the investigation the main parameters of gas turbine engine and auxiliarly systems were measured: gas temperature and pressure at gas turbine and afterburner exit, fuel flow rate, water mass flow rate, inlet air temperature, water temperature in the cooling chamber, mass flow rate, temperature and velocity of exhaust gas-steam mixture in the exit nozzle, oxygen content in the exit jet. The experimental investigation shows that developed IGG system can work very well for indoor fires but need some modifications in application to outdoor fire suppressing.