A letter to the editor was presented which concerned an earlier report on tests used to assign protection factors for two respirator types based on workplace testing. The letter noted that the workplace protection factors at the blast furnace were significantly lower than at the sinter facility and suggested therefore that workplace protection factors may be substantially different in other environments since performance factor is a function of the nature of the pollutant including particle size, morphology and chemical composition. The letter indicated that a protection factor is a function of exposure and noted that the workplace protection factor increases with increasing workplace exposure for both negative pressure and powered air respirators when each data set is analyzed individually. Therefore, it was suggested that a performance factor requirement based on workplace exposures which offers minimal hazard may be unrealistically low. Regardless of which respirator was worn in the original study or how high the workplace exposure was, no in mask exposure exceeded 30 micrograms/cubic meter. This suggests that both respirators offer adequate protection in the sinter facility and glass furnace of the lead smelter, the site of the original study. The letter concludes that efforts to assign protection factor values to various types of respirators serve no useful purpose and may even be misleading. A reply was also provided by the authors of the article in question. They state that assigning protection factors should be based on the determination of workplace protection factors and not upon the results of laboratory testing until a correlation between the two methods can be demonstrated.
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