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Smoke from accidental fires at sites such as scrap yards or tyre disposal facilities typically contains toxic chemicals such as polycyclic aromatic hydrocarbons (PAHs) or dioxins which can result in contamination of crops or grazing land in the vicinity of a fire. The Agency needs a robust easy-to-use atmospheric dispersion model (ADMS) suitable for modelling fires in order to carry out rapid assessments of the likely severity of any contamination caused by smoke from major fires, and any potential food safety implications.
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A special version of the ADMS, to be referred to as ADMS-Fire, will be developed specifically to meet this requirement. ADMS-Fire will be suitable for modelling tyre-fires and similar major fires on open sites.
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During the early stages of a fire, it is usually difficult to gather all the relevant information required for accurate modelling. Therefore, this project will review existing models for fires, as well as all the relevant parameters that affect the emissions, plume rise, smoke plume dispersion and deposition, in order to identify the main sources of uncertainty when modelling smoke plumes. This will highlight which types of input data are most critical for carrying out robust modelling of smoke plumes from open fires. This knowledge will be utilised in the development and design of ADMS-Fire.
Existing modelling techniques that have been applied to the modelling of fires will be reviewed in the first phase of this project. This review will cover the possible variations in the characteristics of the fire itself, modelling of the hot buoyant plume from the fire, plume dispersion and deposition from the plume. Available data that would be required for input parameters such as combustion efficiency, heat of combustion, air entrainment and emission rates of combustion products will be reviewed during this initial phase.
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The second phase will involve carrying out a sensitivity study using ADMS 3 atmospheric dispersion model. This study will assess the sensitivity of dispersion and deposition predictions to variations in selected input parameters including those characterising the fire source. Two broad categories of parameters will be investigated. These are: 'fire parameters' such as fuel characteristics or variable parameters used for fire plume modelling; and 'dispersion and deposition parameters' such as prevailing meteorological conditions.
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The third phase will use ADMS 3 to produce a set of look-up charts of dispersion and deposition for all the combinations of three different fire sizes, different meteorological conditions, surface roughness lengths and smoke particulate diameters.
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Finally, the ADMS-Fire model itself will be developed. This will be based on a streamlined version of ADMS 3 for which data entry will be simplified. The outputs of ADMS-Fire will include:
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ground level concentration of a contaminant in gaseous and/or particulate phases;
<li>wet and dry deposition; and
<li>plume width.</ul>
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Find more about this project and other FSA food safety-related projects at the <a href="http://www.food.gov.uk/science/research/" target="_blank">Food Standards Agency Research webpage</a>.