A safety device used to prevent the flame of flammable liquid vapors from spreading outward. When designing flame retardant internal components, it is based on the medium of different mixed gases, gas composition, pressure drop, length to diameter ratio, and number of bends to design MESG values and achieve a certain flame retardant speed value with regular fillers. When the flame enters the flame arrester, it is cut into many small flame streams by regular flame blocking elements. Due to heat transfer and wall effect, the incoming gas is cooled, making it unable to reach the ignition temperature. Without the ignition temperature, combustion cannot be formed, ultimately extinguishing the flame flow and achieving the purpose of flame blocking.