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Welders are exposed to high levels of metal fumes, which could be resulting in various health impairments. Respirators became a practical protective option in workplaces, as they are lightweight and easy to use. This systematic review attempts to explore the field effectiveness of using respirators to reduce metal particle exposure in workplaces. We reviewed papers published from 1900 to April 2019 in five major bibliographic databases, including Embase, Web of Science, Medline, Scopus, and CINAHL, along with organizational websites to cover gray literature. In total, 983 references were identified from the databases, out of which, 520 duplicates were removed from the EndNote database. The remaining 463 references were screened for their title and abstract. Out of 463, 70 references went through the full-text screening. Finally, eight papers, including 19 workplace respirator studies, satisfied all the inclusion criteria and were reviewed in this report. The geometric means for metal levels in workers’ breathing zone with and without respirators were 9.4 and 1,777 µg/m3 for iron, 1.1 and 139 µg/m3 for lead, 2.1 and 242 µg/m3 for zinc, and 27 and 1,398 µg/m3 for manganese oxide, respectively. Most reviewed studies reported significant differences between measured metal particle levels among workers who worn respirators and who did not. In addition, results showed that N95 provided significantly less protection than elastomeric half facepieces, full-face respirators, and powered air-purifying respirators (p

A two-dimensional heterogeneous mathematical model was developed and validated to study the effect of relative humidity on volatile organic compound (VOC) adsorption onto activated carbon. The dynamic adsorption model consists of the macroscopic mass, momentum, and energy conservation equations and includes a multicomponent adsorption isotherm to predict the competitive adsorption equilibria between VOC and water vapor, which is described by an extended Manes method. Experimental verifications show that the model predicted the breakthrough profiles during competitive adsorption of the studied VOCs (2-propanol, acetone, n-butanol, toluene, 1,2,4-trimethylbenzene) at relative humidity range 0-95% with an overall mean relative absolute error (MRAE) of 11.8% for dry (0% RH) conditions and 17.2% for humid (55 and 95% RH) conditions, and normalized root-mean-square error (NRMSE) of 5.5 and 8.4% for dry and humid conditions, respectively. Sensitivity analysis was also conducted to test the robustness of the model in accounting for the impact of relative humidity on VOC adsorption by varying the adsorption temperature. Good agreement was observed between the experimental and simulated results with an overall MRAE of 12.4 and 7.1% for the breakthrough profiles and adsorption capacity, respectively. The model can be used to quantify the impact of carrier gas relative humidity during adsorption of contaminants from gas streams, which is useful when optimizing adsorber design and operating conditions.