Abstract:In this two part article in its first part models of heavy gas dispersion in the atmosphere are classified and the distinguished groups of models are characterised. In the second part the procedures for the model quality evaluation are described and the main results of model evaluation projects are summarised. Substances released to the atmosphere which have a density greater than the density of the atmospheric air are called heavy gases or dense gases. The dispersion of heavy gases is different from that encountered in the case of neutrally or positively buoyant gases. Specific models have been developed to describe it. The heavy gas dispersion models differ in the complexity and mathematical description. Based on these criteria four main groups of models are distinguished: simple/empirical models, intermediate/integral and shallow layer models, advanced/Lagrangian particle trajectory and Lagrangian puff dispersion models and sophisticated/Computer Fluid Dynamics (CFD) models. This classification is an extension of the classification proposed earlier in the literature.

This is the second paper of a two part review. In its first part mathematical models for atmospheric dispersion of heavy gases are classified and the distinguished groups of models are characterised. In this part procedures for the model quality evaluation are described and the main results of model evaluation exercises and databases with experimental data related to the subject are summarised. The quality of a model is clearly of great importance since the decisions concerning the safety of people, environment are based on model calculations. Attention is focused on activities carried out in the European Union countries and in the USA. These include the work of the groups of researchers called MEG, HGDEG, projects known under the names REDIPHEM, SMEDIS, DATABASE and the model evaluation exercise carried out by the Sigma Research Corporation.

In the event of an accident in an industrial plant, the damage caused by it can be enormous. There may be environmental contamination in a large area. Injured persons may be both employees of the plant staying on its premises and local residents. The control of major accidents is realised by implementing the procedures regarding: safety analysis, emergency and operational planning, effective land-use planning (LUP), strategic environmental assessment (SEA), environmental impact assessment (EIA) and public consultation. The paper presents findings of a case study aiming to analyse selected spatial planning documents prepared at the municipality and SEA reports accompanying them, with regard to hazards of major industrial accidents in six Polish cities. In addition, changes of relevant Polish legislation taking place from 1995 till now are explained referring to European Union (EU) law. This article is the very first to present the situation concerning LUP around hazardous plants in Poland based on such extensive data. The assessment shows that the way of recording the major accident hazards is varied, but legal norms, binding at the time when the documents were drawn up, were met in each of the analysed documents. Changes of relevant Poland legislation were not the only reason for differences in the ways of recording the hazards of major industrial accidents in these documents. The case study has revealed that relevant Polish regulations can be still improved. The results of the study have useful implications for the control of major accidents, spatial policy-making and environmental management.

This paper aims at reviewing the core Polish regulations on land‑use plan­ning (LUP) around hazardous plants and presenting a researcher’s view on the proposal of a ministerial ordinance on safety distance determination from the plants creating a major accident hazard (Seveso establishments). Currently there are no legal regulations concerning the method of safety distance deter­mination from Seveso establishments in Poland. The method of generic‑dis­tances recommended in the Polish guidelines from 2007 is not mandatory. The author stands by her opinion expressed for the first time in 2015 that Polish legal regulations on safety distance determination from Seveso establishments formulated as a ministerial ordinance are indisputably needed. If the ordinance is issued, it will contribute to a more complete implementation of the Direc­tive 2012/18/EU and will allow nationwide unification of the method of safety distance determination. The consequence‑based approach seems a reasonable option in Polish conditions. This researcher suggests an extension of the draft of the ordinance by introducing a reference tool for the mathematical mod­elling of accident consequences. It is also worth considering the introduction of legal norms for the description of areas designed in the spatial planning documents for the location of Seveso establishments.

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