at the Savannah River Site of the United States Department of Energy. It was first developed by the Pacific Northwest National Laboratory (PNNL) in the 1970s. Puff model – Puff is a volcanic ash tracking model developed at the University of Alaska Fairbanks. It requires NWP wind field data on a geographic grid covering the area over which ash may be dispersed. Representative ash particles are initiated at the volcano's location and then allowed to advect, diffuse, and settle within the atmosphere. The location of the particles at any time after the eruption can be viewed using the post-processing software included with the model. Output data is in netCDF format and can also be viewed with a variety of software. More information on the model is available here. Models developed in the United Kingdom ADMS-5 – See the description of this model in the alternative models section of the models accepted by the U.S. EPA. ADMS-URBAN – A model for simulating dispersion on scales ranging from a street scale to citywide or county-wide scale, handling most relevant emission sources such as traffic, industrial, commercial, and domestic sources. It is also used for air quality management and assessments of current and future air quality vis-a-vis national and regional standards in Europe and elsewhere. ADMS-Roads – A model for simulating dispersion of vehicular pollutant emissions from small road networks in combination with emissions from industrial plants. It handles multiple road sources as well as multiple point, line or area emission sources and the model operation is similar to the other ADMS models ADMS-Screen – A screening model for rapid assessment of the air quality impact of a single industrial stack to determine if more detailed modelling is needed. It combines the dispersion modelling algorithms of the ADMS models with a user interface requiring minimal input data. GASTAR – A model for simulating accidental releases of denser-than-air flammable and toxic gases. It handles instantaneous and continuous releases, releases from jet sources, releases from evaporation of volatile liquid pools, variable terrain slopes and ground roughness, obstacles such as fences and buildings, and time-varying releases. NAME – Numerical atmospheric-dispersion modelling environment (NAME) is a local to global scale model developed by the UK's Met Office. It is used for: forecasting of air quality, air pollution dispersion, and acid rain; tracking radioactive emissions and volcanic ash discharges; analysis of accidental air pollutant releases and assisting in