 Study rationale: The main risk factors of COPD are tobacco smoking, biomass smoking and occupational factors. Tobacco smoking is well-known risk factor so tobacco induced COPD is completely established. Nevertheless the meaning of occupational factors which are less famous are equally important. Based on comprehensive literature review ATS endorsed the notion that strong evidence implicates occupational factors as cause of COPD. Occupational COPD takes 19.2 of all COPD patients and 31.1 of never smokers as resulted NHANESIII study. A considerable number of work-related factors have evidence for a causal association with COPD including and of course not limited silica and silicates and aromatic hydrocarbons. Individuals in a variety of occupations and industries such as coal miners, painters, coke workers, tunnel workers, metallurgists, welding workers, transportation workers, builders, farmers are exposed to factors cited above. Despite this the clinical and pathophysiological features of COPD caused by occupational factors are still unclear. 