Effectiveness of directional airflow in reducing containment failures in hospital isolation rooms generated by door opening

Patients with highly infective diseases (e.g. with airborne infections) are placed in negative pressure isolation rooms to limit the spreading of the diseases in hospitals. However, isolation room door opening and subsequent passage can generate substantial transfer of possibly pathogen laden air out of the isolation room through the doorway and hence cause containment failures. It is important to minimize the doorway airflows in order to reduce or possibly prevent containment failures altogether. This study examined the effectiveness of directional airflow towards isolation room in reducing air transfer through the doorway caused by hinged door opening, passage and temperature difference. Smoke visualizations illustrated qualitatively that directional airflow towards the isolation room, lasting the entire door cycle, was able to limit the air transfer notably. The tracer gas measurements showed that 90 L/s directional airflow reduced the air volume escape out of the isolation room by 38% in isothermal conditions and by 31% with 3 °C temperature difference between the rooms compared to cases without directional airflow. Higher directional airflow rate of 190 L/s reduced the air transfer by 60% in isothermal conditions and by 39% with 3 °C temperature difference. Although the tested directional airflow rates did not totally prevent the air escape they appeared to be effective in reducing the door opening, passage and temperature difference induced air exchange through the isolation room doorway. •The effectiveness of directional airflow in reducing door opening induced air escape was studied.•Directional airflow reduced the air escape substantially in isothermal conditions.•The method worked well also with temperature difference between rooms.•This method can be applied to hospital isolation rooms to reduce containment failures.