In urea plants passivation air is used in reactor, stripper and downstream of the all equipments. The reactor liner material used can be Titanium, Zirconium, SS 316L (urea grade), 2RE-69 and duplex material. Except Titanium and Zirconium all stainless steels required more passivation air. In CO2 some quantity of hydrogen is present; about 0.14-0.2vol%. The passivation oxygen and hydrogen makes an explosive mixture. To avoid a fire or explosion in a process vessel one introduces inert (noncombustible) gases in such a way that there is never a mixture with a combustible concentration in the exit of the MP vent. Mixtures of fuel, oxygen, and inert gases are not combustible over the entire range of composition. In the CO2 stripping process the HP scrubber is the risky vessel and this vessel consists of a blanketing sphere, heat exchanger part and a scrubbing part. With help of triangular diagram that shows the shape the of combustible/noncombustible regions for a typical gaseous mixture of fuel, oxygen, and inert at specified temperature and pressure. Present articlee laborates how to avoid that combustible rang and how to tackle that gases in the CO2 and ammonia stripping process.