中文摘要：

目的研究不同环境条件下，N95型自吸过滤式防尘口罩和普通医用口罩对细菌防护效果的差异，分析影响口罩对细菌滤过性能的因素。方法通过现场佩戴测试，在夏冬两季不同工作环境下各选取12名受试者先后佩戴N95口罩和普通医用口罩各1h，检测口罩内外表面细菌浓度和环境空气细菌浓度，分析两种口罩防护效果的差异。通过过滤效率测试比较两种口罩对细菌的过滤效率。结果在20L／min流量下测得N95口罩和医用口罩对细菌的平均过滤效率分别为99．93％和91．53％，差异有统计学意义（P〈0．01）。夏季环境空气细菌浓度高于冬季，同一季节医院环境空气细菌浓度高于校园环境，在空气细菌浓度越高的环境佩戴的口罩外表面染菌量越大。在不同工作环境中，N95型口罩和一次性医用口罩外表面染菌量均明显高于内表面，差异有统计学意义（P〈0．01）。在同一工作环境中，与N95型口罩比较，一次性医用口罩外表面染菌量较低，内表面染菌量较高，但差异无统计学意义（P〉0．05）。在所有工作环境中佩戴的N95型口罩对细菌的过滤比例均高于一次性医用口罩，夏季时，差异有统计学意义（P〈0．05），冬季时，差异无统计学意义（P〉0．05）。结论N95型口罩对细菌颗粒的防护效果略优于一次性医用口罩，在空气细菌浓度较高的环境中优势更明显。

英文摘要：

Objective To determine the relative protection provided by N95 filtering faeepiece respirators （FFR） and disposable medicine masks （DMM） against airborne bacteria in different working environments. Methods The field study was performed with 12 subjects wearing an N95 filtering facepieee respirator and a disposable medicine mask for lh, respectively. Airborne microorganisms and bacteria samples from both the external （Ce） and the inner （Ci） surface of N95 FFR and DMM are collected. The Ce： Ci ratio was used to calculate the bacterial filtering proportion. Bacterial filtering efficiency （BFE） was measured using the JWL-2A Sampler. Results The bacterial filtration efficiency of N95 FFR and DMM were 99.93% and 91.53%, respectively. There was significant difference between the two materials （P〈O.05）. In summer, airborne bacterial concentration was higher than that in winter. In the same season, airborne bacterial concentration in hospital environment is higher than that in campus. Tile higher the airborne bacterial concentration, the greater bacterial contaminated on the external surface of the used masks. To all masks used in different working environment, bacterial contamination on the external surface was much greater than the inner surface （P〈0.01）. Compared to N95 FFR, DMM had slighter bacterial contamination on the external surface and greater bacterial contamination on the inner surface. However, this difference was not significant （P〉0.05）. The bacterial filtering proportion of N95 FFR is higher than DMM. These differences were significant in samples tested in summer （P〈0.05）, but were not significant in samples tested in winter （P〉0.05）. Conclusion Bacterial filtering efficiency of N95 respirator is superior to medicine mask, and this advantage become more obvious in high airborne bacterial concentration levels.