Nicas M, Miller S L
Center for Occupational and Environmental Health, School of Public Health, University of California, Berkeley, USA.
Appl Occup Environ Hyg. 1999 May;14(5):317-28. doi: 10.1080/104732299302909.
Engineering controls can be used to reduce the spread of airborne infectious disease, particularly tuberculosis (TB), in high-risk settings. This article evaluates published data on the efficacy of upper-room air ultraviolet germicidal irradiation (UVGI). A three-zone representation of a TB patient room equipped with a germicidal UV lamp is developed. The lamp irradiates the upper-room zone and inactivates airborne mycobacteria; the unirradiated lower-room zone also contains a near-field zone surrounding the TB patient. Infectious particles are generated in the near-field zone and transported throughout the room by air flow between zones. Each zone is independently well-mixed; the whole room, however, is not well-mixed. The three-zone model is applied to a previously published study of UVGI against airborne mycobacteria in a test room. Based on the estimated slopes of the semi-log concentration decay curves for viable mycobacteria, and on the assumption that the test room was essentially well-mixed, the published study reported that UVGI provided 10 to 25 equivalent air changes per hour. However, when the same decay curve slopes are interpreted in the context of the three-zone model, UVGI is seen to be far less effective in reducing exposure intensity near the TB patient. Near-field exposure intensity is relevant because health care workers are usually in close proximity to the TB patients they attend. In general, the interpretation of concentration decay data depends on the specific model of room air mixing that is assumed appropriate. It is recommended that tests of the efficacy of UVGI and other control devices against airborne microorganisms be based on steady-state concentration measurements rather than concentration decay measurements, because the former measurements do not require inferences based on a particular model.
工程控制措施可用于在高风险环境中减少空气传播传染病，尤其是结核病（TB）的传播。本文评估了已发表的关于上部空间空气紫外线杀菌辐照（UVGI）效果的数据。建立了一个配备杀菌紫外线灯的结核病患者病房的三区模型。该灯照射病房上部区域，使空气中的分枝杆菌失活；未照射的病房下部区域还包括围绕结核病患者的近场区域。感染性颗粒在近场区域产生，并通过区域间的气流在整个病房内传播。每个区域各自充分混合；然而，整个病房并未充分混合。将三区模型应用于先前发表的一项关于在测试病房中UVGI对空气中分枝杆菌作用的研究。基于对存活分枝杆菌的半对数浓度衰减曲线估计斜率，并假设测试病房基本充分混合，该发表的研究报告称UVGI每小时提供10至25次等效换气次数。然而，当在三区模型的背景下解释相同的衰减曲线斜率时，UVGI在降低结核病患者附近的暴露强度方面效果要差得多。近场暴露强度很重要，因为医护人员通常与他们护理的结核病患者距离很近。一般来说，浓度衰减数据的解释取决于所假设的合适的病房空气混合具体模型。建议对UVGI和其他控制装置针对空气传播微生物的效果测试基于稳态浓度测量而非浓度衰减测量，因为前者测量不需要基于特定模型进行推断。
