Fuel Processor mitigating CO2 emissions being suspected of contributing to the so called global warming caused by the use of fossil fuels and having a high energy conversion efficiency produces H2 through Reforming technology using LNG, LPG and Naphtha and supplies Fuel Cell System with them. Especially, many major Korea companies utilize Reforming technology using NG. In this study, a quantitative and qualitative risk analysis is performed and from that results, we estimated the Explosion-proof optimal ventilation rate considering physical and chemical dangers of H2 from the worst Case scenario with H2 gas leakage in the case of having various ignition sources such a spark and arc by electric installations in explosiveness conditions mixing with O2 in the atmosphere. CO2 (Fuel Processor) LNG, LPG, Naphtha , Reforming H2 (Fuel Cell System) NG Reforming .