Metal impurity removal from gaseous stream

A method and apparatus for the removal of sodium magnesium, iron, nickel and chromium from a gaseous stream wherein the apparatus or trap comprises an unlined pipe 136 which is at least 45.7 cm (18 inches) long, a heated pipe 114, a cooled pipe 109 connected to the heated pipe and an injection point 101. In use, a gaseous stream containing sodium is conducted through the unlined pipe 136 and a neutralizing agent is injected into the gaseous stream at an injection point 101, wherein the injection point is located at a point where the sodium is in at least a partially condensed state. The gaseous stream is then conducted through the heated pipe 114 and the cooled pipe 109. The neutralizing agent maybe carbon dioxide (CO2), water, steam or nitrous oxide (NO2). The trap is connected to a carbonization furnace and the gaseous stream results from the sublimation of sodium and other impurities during a carbon fibre production process. The removal of these impurities prevents fouling and corrosion of downstream components.