The ventilation performance of airborne infection isolation rooms (AIIRs) was assessed in three Finnish hospitals by examining the air change rate, contaminant removal efficiency and leakage of contaminants outside the isolation room by using tracer gas techniques. Results showed that infectious agents can escape from the AIIR during egress despite high ventilation rates in the AIIR and anteroom (air change rate, 4–24 h−1) and the pressure difference between the AIIR and corridor was −0.2 to −29 Pa. The control of impurities was often ineffective due to inappropriate direction of air flows and air moving from the patient towards the health care worker and anteroom. Although an anteroom reduces leakage of infectious agents to the corridor significantly, it does not prevent this completely when healthcare workers move between the AIIR and corridor. To enhance the protection of AIIRs, it is especially important to pay attention to the air distribution and removal efficiency of impurities in AIIRs and anterooms. Performance of AIIRs should be tested regularly, especially among older AIIRs.

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Improvement on implementation of dust controls is required through revising the guidance documents, education, and efficient supervision. This study revealed that the current Finnish practice to implement the negative pressurization based on the air exchange rate achieved with the portable exhaust fans alone is not reasonable to assure adequate dust containment. Continuous negative pressure minimum of -5 Pa is suggested, and it should be monitored with alarm devices throughout the renovation processes.

The aim of the study was to find out good practices for effective air distribution inside a complex shaped asbestos enclosure and for control of pressure differences between the enclosure and the surroundings. In addition, sufficient pressure difference for asbestos containment was tested. The effect of air distribution was studied in laboratory conditions by constructing an L-shaped asbestos enclosure and connecting it to a negative pressure unit. The efficiency of six different ventilation configurations was compared using a tracer decay method and the local air change indexes as the performance indicator. The sufficient negative pressure for containment was assessed by simulating person traffic to and from the enclosure and recording the pressure difference continuously. The effect of a pressure controller unit in maintaining the target pressure difference was also tested by simulating filter loadings of the negative pressure unit causing changes in the air flow rate. The results showed that high nominal air change rates alone do not guarantee good air distribution. Effective air distribution within an asbestos enclosure can be arranged by locating additional air supply openings far away from the air exhaustion point, using recirculation air with a pressure controller, or extending the exhaust location to the poorly ventilated areas. A pressure difference of at least −10 Pa is recommended to ensure a sufficient margin of safety in practical situations.

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