Demand-controlled ventilation systems

Demand-controlled ventilation systems use sensors to detect the level of occupancy, water vapour or other pollutants and adjust the ventilation rate to avoid over-ventilation. In dwellings, humidity-controlled devices are available to regulate the humidity of the indoor air and, hence, minimise the risk of condensation and mould growth. In buildings other than dwellings more sophisticated automatic control systems are available. These may be based on sensors located within the building (e.g. occupancy sensors using local passive infra-red detectors) or indoor carbon dioxide concentration sensors (using electronic carbon dioxide detectors) as an indicator of occupancy level and, therefore, body odour.