Ventilation and health – a review

People in industrialised countries spend about 90% of their time indoors. Hence, a good indoor climate is essential for health and well-being. Ventilation of buildings plays an important role concerning health aspects of the occupants and inadequate ventilation may cause health costs that may have been avoidable if ventilation would have been adequate. Additionally, good or bad ventilation has impacts on the quality of the building, e.g. in very tight buildings, the risk of mould and dampness is higher if air change is insufficient. This paper focuses on the influence of different types of ventilation systems and ventilation rate on occupant’s health in homes and schools. A literature search has been conducted to review the influence of ventilation on different health outcomes.
Most of the studies were found for the influence of natural vs. any type of mechanical ventilation on different health indicators. But the results of the different studies are not consistent. The reason for this may lie in the sometimes slightly but often considerably different ventilation variables that are evaluated. Studies report e.g. on the one hand that in naturally ventilated day care centres, the prevalence of asthma symptoms and rhinitis decreased whereas in another studies mechanical ventilation systems reduce eye and nasal irritation symptoms as well as tiredness. There are also studies that report no differences between the usage of natural vs. mechanical ventilation systems. One main weak point of many studies is that variables that may bias the results are not indicated, e.g. the state of the filters used. Two studies were designed as intervention study and they investigated the influence of heat recovery ventilators on asthma and respiratory disorders. Wheeze and rhinitis were found considerably lower in homes with heat recovery ventilators.Low ventilation rates promote the development of allergies and respiratory diseases like wheeze or cough (OR between 1.3 and 2.39). In schools, ventilation rates are often below the recommended values (e.g. about 0.9 to 3 l/s instead of 8 l/s per person) and may therefore ease illness of pupils and teachers.
The following conclusions may be drawn from this work: First, a higher ventilation rate promotes health and attention should be drawn on the achievement of sufficient ventilation rates, especially in schools. Focused research should give a more detailed insight into this relationship. Second, the influence of the type of ventilation system is ambiguous with respect to the outcome. No clear recommendation for natural or mechanical ventilation could be derived from the available studies. More consistent data is needed with better documentation of confounding variables to consider causal relationships.