An Evaluation of the Ventilation Performance of New SARS Isolation Wards in Nine Hospitals in Hong Kong

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Abstract
In response to the 2003 outbreak of severe acute respiratory syndrome (SARS) the Hong Kong Government promptly constructed 558 new state-of-the-art SARS isolation rooms with more than 1300 beds in 14 hospitals. These were completed by the end of 2003 and some will be available for H5N1 influenza patients, if any human cases occur. We investigated the ventilation of the wards after 18 months of operation and identified the major factors that affect ventilation effectiveness. Negative pressure, airflow path, air change rate and local ventilation effectiveness in selected rooms in 9 major hospitals were measured and their performance assessed against CDC requirements. Testing in 38 rooms found that 97% met the recommended negative pressure difference of 2.5 Pa between corridor and anteroom, 89% of 48 met the same requirement between anteroom and cubicle. No leakage of air to the corridor was found, but 60% of the toilets/bathrooms were operated under positive pressure. Over 90% of corridor-anteroom or anteroom-cubicle doors had bi-directional flow when the door was open. Of 35 tested cubicles, 26% had an air change rate <12 ACH and their ventilation was non-uniform. Despite using state-of-the-art technologies, 28% of the rooms tested still failed to meet the 12 ACH ventilation requirement and 60% had the wrong airflow direction for the toilets/bathrooms, but all satisfied the requirement of no air leakage to the corridor. Regular checks of airflow direction and air change rate are highly recommended together with specific education or training of hospital maintenance engineers and health care workers.