This paper describes the tools and services provided by a national centre for modelling the environmental and health impacts of airborne hazardous materials. This centre can provide emergency decision support information within minutes for a wide range of radiological, nuclear, chemical, and biological hazards from fires, industrial and transportation accidents, radiation dispersal device explosions, hazardous material spills, nuclear power plant accidents and nuclear detonations. Web- and internet-based software provides quick access to advanced modelling tools, as well as expert analyses from the centre. Model predictions include the 3D spatial and time-varying effects of weather, land use and terrain, on scales from the local to regional to
global. Tools provide displays of plume predictions with affected population counts, detailed maps, and reports describing model assumptions,
contamination and dose levels. On-scene information and measurements are used to refine model predictions.