First off switch or to close the valve

Gas stove: First off switch or to close the stove valve?
Gas stove switch that switches on the gas stove safety, and now the general and ignition function together. Gas stove valve refers to a valve on the pipe connecting the stove, ventilation rotated 90 degrees, 90 degrees reverse turn off the gas.
So, turn off the heat when it should turn off the valve on a gas stove, because, if the first switch off the stove, may be mixed with air in the pipe connecting the stove again when the ignition could cause an explosion.