Opening windows can be more effective than using mechanical ventilation at reducing the risk of transmission of airborne diseases such as tuberculosis (TB) – a study funded by the Wellcome Trust and the Sir Halley Stewart Trust.
The spread of airborne infections in institutional settings such as hospitals, waiting rooms, prisons and homeless shelters is an important public health problem. This is especially true in resource poor settings, where the prevalence of TB is highest, and where preventive measures such as negative-pressure isolation rooms are hardest to implement.
A study published today in the journal PLoS Medicine and carried out by researchers from the Department of Infectious Diseases and Immunity and the Wellcome Trust Centre for Clinical Tropical Medicine, Imperial College London, is the first to investigate the role of natural ventilation by opening windows and doors for preventing the transmission of airborne infection. This simple and low-cost measure is recommended by the WHO for preventing TB transmission in healthcare settings, but until now there have been no studies to support these guidelines.
The researchers, led by Dr. Rod Escombe from Imperial College London, studied eight hospitals in Lima, Peru, and measured natural ventilation in 70 different rooms where infectious patients are likely to be found, including respiratory isolation rooms, TB wards, respiratory wards, general medical wards, outpatient consulting rooms, waiting rooms, and emergency departments. They compared these with 12 modern mechanically-ventilated, negative-pressure respiratory isolation rooms.
The study found that natural ventilation when windows and doors were opened was more than double that of mechanically-ventilated, negative-pressure rooms functioning at the high rates recommended by guidelines, and 18 times that of rooms with windows and doors closed. Even at the lowest wind speeds, natural ventilation exceeded mechanical ventilation.