Effects on gas explosion behavior of gas flow turbulence, combustible gas concentration distribution, and flame front instability, which are the most probable causes that disturb the propagating flame front during gas explosions, have been examined. Qualitative aspects of these effects had already been examined in our previous experimental studies. In this paper, data measured in these studies were analyzed quantitatively. It is shown that the gas flow turbulence increases the flame propagating velocity and this makes the pressure rise rapid. When the gas flow turbulence exists the pressure rise from the initial pressure is observed to be proportional to about the 3.6th power of the time t from ignition, whilst if no gas movement exists it is proportional to the 3rd power of t. When the concentration of a combustible gas was non-uniform, the gas explosion behavior strongly depends on the concentration distribution. The flame front becomes unstable by acceleration of the gas induced by a following pressure wave propagating toward the unburned gas side and generated flame front disturbance grows quickly, so that the flame propagating velocity increases rapidly. Then a fast pressure rise is observed and it is proportional to the 6.4-6.8th power of t.