Evaluating IAQ effects on people

Following a comprehensive review of research over the 150-year history of mechanical ventilation, the recent European Multidisciplinary Scientific Consensus Meeting (EUROVEN) considered that only 20 studies relating ventilation (i.e. outside air supply rate per person) to human response were "conclusive". From them, a small number of conclusions were drawn, and some very large gaps in our knowledge of this important area of research were identified. Taking these as the starting point, this paper formulates a strategy for evaluating IAQ effects on people. It formulates some critical hypotheses and recommends appropriate research methodology for testing them. The first goal is to prove causation, the second is to identify the mechanisms of causation and the third is to assess the magnitude of the resulting positive or negative effects. Cross-sectional studies prove association, not causation, and it will thus be necessary to perform field intervention experiments. Economic, ethical and commercial considerations often make it impossible to perform the reversible interventions that are necessary to eliminate confounding. A neglected alternative is randomized scheduling of upgrades that would have been performed anyway. This powerful research strategy need not increase costs, is as ethically defensible as a clinical trial and will usually be commercially acceptable.