The Model NK-FT23A is used to protect low pressure waste gas systems if a fire is burning in the piping. The flame trap is a valve intended to prevent backfiring of inflammable mixture of air and vapor and gas etc. automatically. The flame trap assembly serves to extinguish a fire occurring in sewage and other facilities where methane gas is apt to be produced. When the gas catches fire, the valve is closed by the generated heat to stop the gas flow. The Flame Trap is generally installed in gas lines leading from each digester and gas holder. It is also installed in a line to gas utilization equipment, as close as possible to the source of combustion.