AIRBORNE INFECTION - THEORETICAL LIMITS OF PROTECTION ACHIEVABLE BY BUILDING VENTILATION
AIRBORNE INFECTION - THEORETICAL LIMITS OF PROTECTION ACHIEVABLE BY BUILDING VENTILATION
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DOI：
10.1164/ajrccm/144.2.302
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发表时间：
1991-08-01
期刊：
影响因子：
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通讯作者：
ETKIND, SC
中科院分区：
文献类型：
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作者：
NARDELL, EA;KEEGAN, J;ETKIND, SC
在67名办公室工作人员中，27人（40%）在与患有腔型结核病的同事接触约4周后，记录了结核菌素皮肤试验的转变。在肺结核接触前2年多的工人投诉促使对肺结核接触前后建筑物的空气质量进行调查。建筑物许多地方的二氧化碳浓度都高于建议水平，表明室外空气通风不佳。我们将空气传播的数学模型应用于数据，以评估建筑物通风和其他传播因素的作用。我们估计，与外部空气的通风平均约为每个乘员15英尺3/分钟（cfm），可接受的通风的低端，对应的二氧化碳水平约为1000ppm。该模型预测，在人均25 cfm时，将有18名工人被感染（减少33%），而在35 cfm（被认为是最舒适的水平）时，将有13名工人被感染（再减少19%）。进一步增加室外空气流通是不切实际的，而且会导致保护的增量逐渐减少。根据该模型，在暴露期间，指数病例每小时向办公室空气中增加了大约13个感染剂量（量子），是大量结核病病例报告的平均传染性的10倍。进一步的模型预测，随着传染性的上升，通风提供的保护将逐渐减少。我们得出的结论是，室外空气通风不够舒适可能会导致空气传播感染，但高于舒适水平的通风对建筑物居住者的保护可能是有限的，特别是当暴露于感染水平较高时。
Of 67 office workers 27 (40%) had documented tuberculin skin test conversions after an estimated 4-wk exposure to a coworker with cavitary tuberculosis. Worker complaints for more than 2 yr before the tuberculosis exposure prompted investigations of air quality in the building before and after the tuberculosis exposure. Carbon dioxide concentrations In many parts of the building were found to be above recommended levels, indicating suboptimal ventilation with outdoor air. We applied a mathematical model of airborne transmission to the data to assess the role of building ventilation and other transmission factors. We estimated that ventilation with outside air averaged about 15 feet3/min (cfm) per occupant, the low end of acceptable ventilation, corresponding to CO2 levels of about 1,000 ppm. The model predicted that at 25 cfm per person 18 workers would have been infected (a 33% reduction) and at 35 cfm, a level considered optimal for comfort, that 13 workers would have been infected (an additional 19% reduction). Further increases in outdoor air ventilation would be impractical and would have resulted in progressively smaller increments in protection. According to the model, the index case added approximately 13 infectious doses (quanta) per hour (qph) to the office air during the exposure period, 10 times the average infectiousness reported in a large series of tuberculosis cases. Further modeling predicted that as infectiousness rises, ventilation would offer progressively less protection. We conclude that outdoor air ventilation that Is inadequate for comfort may contribute to airborne infection but that the protection afforded to building occupants by ventilation above comfort levels may be Inherently limited, especially when the level of exposure to infection is high.