The indexed assessment of fumes generated by high power laser material processing

The nature of the fume generated by high power laser processing is dependent upon laser type, material being processed, assist gases used, and the energy density required to process the material. The fume produced from any one process will vary in its composition, aerosol size distribution, morphology, and toxicity, all of which are important factors when assessing human and environmental hazards. At present no straightforward method exists to estimate the hazards. In this article a method for indexing the hazards of fumes generated by laser materials processing is presented. The index can be applied to a wide range of materials and laser processing techniques and should lead to a standardization of information pertaining to laser-generated fumes. Two parameters are applied to describe the fumes hazard. The first parameter is the exposure limits, which indicates the perceived hazard of an individual component released during processing. The exposure limits used are the UK long-term occupational exposure standards and the maximum exposure limits. The second parameter is the component production rate from a standard material, i.e., the weight emitted per second (mg/s) of each species during cutting. By combining these parameters, the Normal Air Requirement (NHL) for each component can be calculated. The individual NHLs are then summed to produce an NHLtot. These NHLtot’s serve as guidelines to the hazard since they are highly dependent upon processing criteria and are weighted in this application to particulate emissions. They are also derived from continuous measurements, whereas in real applications the downtime during a working day is considerable. From the NHLtot a classification system can be constructed which can be used to indicate the type of filtration and extraction necessary to effectively deal with the laser processing emissions.