When the incandescent lamp works, the filament is in a high-temperature incandescent state. If the filament temperature is too high, the tungsten filament will evaporate too quickly and its life will be reduced. And the evaporated tungsten is deposited on the inner wall of the bulb, which will make the bulb black and affect the brightness. After the bubble shell is filled with a proper amount of inert gas, the evaporation ratio of tungsten wire under a certain pressure is greatly reduced compared with that in vacuum. That is to say, under the same life, the working temperature of the filament of the inflatable bulb can be higher than that in vacuum, thus improving the luminous efficiency. Therefore, after vacuumizing, incandescent bulbs are usually filled with argon, nitrogen or argon-nitrogen mixed gas at a certain pressure.