Indoor air pollution has received less attention than outdoor air pollution. This is explained, in part, by the clearly visible coal smoke smogs of 50 years ago and the photochemical smogs of today, and also, by the perception that outdoor air pollution is the Government's business whereas indoor air is not. Great strides have been made in improving outdoor air: that indoor air has improved in parallel may be doubted. All occupational and environmental physicians know that sick building syndrome, legionnaire's disease, and multiple chemical sensitivity are conditions that have come to prominence recently. Dealing with sick building syndrome and multiple chemical sensitivity is not easy and an authoritative source of advice has long been …