Filtration of laser generated air contaminants

Over the last few years, the knowledge about laser generated air contaminants (LGAC) has increased greatly. For many laser applications (cutting, welding, material removal, marking, etc.), and different materials - metals, ceramics and polymers, the emission product rates and their chemical composition have been analysed. The characteristics of LGAC are heterogeneous composition with smallest aerosol particles and a large number of gaseous substances. Occupational assessment studies show that gaseous and particulate air contaminants can cause health hazards. To avoid potential hazards to humans and the environment, and to keep within prescribed threshold limit values, the exhaust air from laser material processing plants must be filtered. In addition, bad odors during laser processing of organic materials (plastics, wood, leather, etc.) due to various hydrocarbons are a problem in many cases. Because of these specific properties, LGACs require specific technical solutions for effective filtration. Within several research projects at the Laser Zentrum Hannover e.V., different filtration techniques for volatile organic components (VOC) and aerosol emissions have been investigated. This paper summarizes the results of pilot studies with industrial storage, surface, electrostatic and wet filter systems for aerosol emissions and the filtration of gaseous emissions with catalytic combustion, biological filtration and adsorbtive techniques. The advantages and disadvantages of the systems investigated will be discussed. Based on filtration efficiencies and economical aspects, recommondations on the selection of filtration techniques will be given according to the laser process and materials used.