Noble gases are also called noble gases, including helium, neon, argon, krypton, xenon and radon. Their air volumes are argon 0.94%, neon 0.0018%, helium 0.0005%, krypton 0.00011%, and xenon 0.000009%, respectively. Radon is a radioactive gas. Because their content in the air is very small, they are called noble gases. Under normal circumstances, noble gases are chemically inactive and do not react easily with other substances. They are also called noble gases. According to their nature, noble gases are used in production and scientific research. Helium, which cannot burn, is light enough to fill high-altitude balloons and airships instead of flammable hydrogen. Because the chemical properties of rare gases are very inactive, they are commonly used as protective gases in industrial production. For example, when welding stainless steel and aluminum alloy materials used in rockets, airplanes, missiles, ships, etc., high-purity argon can be used as protective gas to prevent metal and oxygen in the air from reacting at high temperature. A common incandescent bulb is filled with a mixture of argon and nitrogen gas to protect the filament and extend the life of the bulb.