When the gas fire, you should first close the valve, what fire works?

Cut off fuel.
Extinguishing principle of water: the water itself does not burn, cover the surface of the combustible material to absorb a lot of heat, the temperature of fuel drastically reduced to less ignition point, and water vapor produced in the combustible surface covering, also played a cut off the air role.
Carbon dioxide fire extinguishing principle: because of the carbon dioxide itself does not burn or support combustion, density greater than air, played the role of isolated air, without oxygen naturally extinguish the fire.
Overall, biomass burning have two conditions: a temperature drop below the ignition point, the absence of air between two indispensable fire, meet one of the conditions, the fire can be extinguished.!