Comparing indoor air quality in naturally ventilated and air-conditioned hospitals in the tropics

Occupant exposure to airborne pathogens in buildings can be reduced by a variety of means, including adequate provision of outdoor air by ventilation. This is particularly important in buildings, such as hospitals, which may house a higher number of infected individuals relative to the wider population. In tropical Africa, however, there is evidence that new hospitals built with air-conditioning to cope with the extreme heat are poorly ventilated compared to existing hospitals that were designed to be naturally ventilated. As a proxy for indoor air quality, the carbon dioxide concentrations in two hospitals in Ghana were monitored over a period of one week. All wards were naturally ventilated, but some also had mechanical ventilation or recirculating air-conditioning. Air-conditioned wards generally had the poorest indoor air quality, with measured maximum CO2 concentrations of 3286 ppm indicating insufficient ventilation relative to occupancy levels. Staff reported keeping windows closed in these wards to prevent mosquitoes from entering and to provide thermal comfort for the patients. Recommendations are that staff working in air-conditioned rooms should regularly open windows to allow outdoor air to enter. Mosquito netting should be installed on all windows to encourage staff to open the windows. Future hospital design should better consider the interplay between thermal comfort, ventilation, and indoor air quality.