The dust comes from the metal processing will be sucked into the collector via the hood, firstly, the fume passes the 1st layer spark intercept steel mesh which will filter the spark to avoid residual sparks enter into filter cartridge directly. Finally, the fume enters the second layer of HEPA filter cartridge for filtration. Its filtration efficiency can reach 99.9%. As the filtering precision of the main filter cartridge reaches the indoor emission standards, the filtered clean air can be directly discharged indoor through the air vent in the back of the extractor. According to the amount of dusts and extractor's work intensity, the usage life of the filter cartridge is different.