Indoor air pollutants have a significant impact upon the occupants’ health. Dust-mite allergens are a major factor in the development and provocation of asthma as are mould spores and metabolites. Formaldehyde and volatile organic compounds are irritants especially to the eyes and the respiratory tract and some are carcinogenic. Combustion products including particulates and oxides of nitrogen, carbon and sulphur are variously irritants, respiratorily provocative or carcinogens. This research is aimed at understanding the behaviour of these pollutants and providing mitigation measures to provide healthy, safe and comfortable indoor environments to all New Zealanders.We intend to achieve this by arriving at a deeper understanding of the behaviour of these pollutants in our indoor environment, by the development of a very broad thoroughly validated indoor environment tool (called BRANZIAQ) that will model the indoor physical processes of pollutant generation, emission, dilution and transport and explore how these are modified with products and systems such as dehumidifiers or mechanical ventilation systems.The model will consist of a number of linked sub-models viz.: an indoor climate and microclimate sub-model; biological population dynamics sub-models to follow the growth and decline of biocontaminants, particularly mould and dust-mites; an aerosolisation sub-model for biocontaminants; a surface mass transfer sub-model for the release of inorganic and organic pollutants into the room air; an intra-room computational fluid dynamics (CFD) sub-model for contaminant movement into the breathing zone; and an inter-room zonal sub-model to assess whole house performance. Human dose-response sub-models could follow at a later date. As an example of what the model can do, and as one method for validating the model, we will develop a new high efficiency domestic dehumidifier and test its performance in the field and compare that to BRANZIAQ predictions. Domestic dehumidifiers do not always perform well in cold New Zealand houses but adding an economiser should improve their efficiency. The whole-house performance of the domestic dehumidifier will be tested against BRANZIAQ predictions and BRANZIAQ modified where necessary. Towards that outcome we aim to have BRANZIAQ implemented by: embedding it or design tables generated by it in the Means of Compliance Documents that support the new Building Code under development by the Department of Building and Housing; used by Appraising and Certifying agencies; used by manufacturers for product development; and used by designers; etc.The programme is at an early stage but progress is on track. We have selected the major sub-models for BRANZIAQ: PHOENICS is the central computational fluid dynamics (CFD); Energy+ is the building energy simulation program; and DesignBuild is the user friendly interface to these programs.One in-house sub-model has been written in dust-mite population dynamics and a paper describing this has been accepted by “Medical Entomology”. Searching for the best dust-mite population model is an internationally active field at the moment. Our model is the first one published to take into account the fluctuating relative humidities and temperatures found within the dust-mites microenvironments in bedding, the base of carpets and soft furnishing, and the first to take into account the limited carrying capacity of these environments. This builds on earlier pioneering work of this team in developing the instrumentation that allowed the relative humidity and temperature microenvironments to be measured.Some preliminary data has been gathered on the rate and size of particulates aerosolised when walking over carpeted and uncarpeted floors which will be used to help develop and validate a particulate sub-model for BRANZIAQ.To show BRANZIAQ in action we are developing a new high efficiency domestic dehumidifier, which will have its in-service performance compared to BRANZIAQ prediction. Towards building a prototype of this dehumidifier a calorimeter has been built to characterise the performance of compressors taken from existing commercial domestic dehumidifiers.