Many UK hospitals rely heavily on natural ventilation as their main source of airflow in patient wards. This method of ventilation can have cost and energy benefits, but it may lead to unpredictable flow patterns between indoor spaces, potentially leading to the unexpected transport of infectious material to other connecting zones. However, the effects of weather conditions on airborne transmission are often overlooked. A multi-zone CONTAM model of a naturally ventilated hospital respiratory ward, incorporating time-varying weather, was proposed. Coupling this with an airborne infection model, this study assessed the variable risk in interconnected spaces, focusing particularly on occupancy, disease and ventilation scenarios based on a UK respiratory ward. The results suggest that natural ventilation with varying weather conditions can cause irregularities in the ventilation rates and interzonal flow rates of connected zones, leading to infrequent but high peaks in the concentration of airborne pathogens in particular rooms. This transient behaviour increases the risk of airborne infection, particularly through movement of pathogens between rooms, and highlights that large outbreaks may be more likely under certain conditions. This study demonstrated how ventilation rates achieved by natural ventilation are likely to fall below the recommended guidance, and that the implementation of supplemental mechanical ventilation can increase ventilation rates and reduce the variability in infection risks. This model emphasises the need for consideration of transient external conditions when assessing the risk of transmission of airborne infection in indoor environments.

中文翻译：

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评估瞬态天气条件对自然通风医院空气传播风险的影响


许多英国医院严重依赖自然通风作为病房气流的主要来源。这种通风方法可以带来成本和能源效益，但它可能会导致室内空间之间不可预测的流动模式，从而可能导致传染性物质意外输送到其他连接区域。然而，天气条件对空气传播的影响常常被忽视。提出了自然通风医院呼吸病房的多区域 CONTAM 模型，其中考虑了随时间变化的天气。将其与空气传播感染模型相结合，本研究评估了互连空间中的可变风险，特别关注基于英国呼吸病房的占用、疾病和通风情况。结果表明，不同天气条件下的自然通风可能会导致相连区域的通风率和区间流速不规则，从而导致特定房间中空气传播病原体浓度出现罕见但很高的峰值。这种短暂的行为增加了空气传播感染的风险，特别是通过病原体在房间之间的移动，并强调在某些条件下更有可能发生大规模爆发。这项研究证明了通过自然通风实现的通气率可能会低于建议的指导值，而实施补充机械通气可以提高通气率并降低感染风险的变异性。该模型强调在评估室内环境中空气传播感染传播的风险时需要考虑短暂的外部条件。