On-site emergency planning and the use of predictive techniques

Abstract

Abstract Good safety management requires hazard elimination and reduction where possible, containment to protect people and the environment, and as a last resort carefully considered and well practised emergency procedures to mitigate the effects of possible major accidents. The preparation of an emergency plan requires an understanding of the properties of the raw materials, intermediates, products and by-products, the process and storage conditions, and the desired and potential undesired reactions. Using these data and postulating various release mechanisms, a full range of scenarios can be developed to represent the potential consequences of major accidents involving fire, explosion, toxic gas and/or damage to the environment. The development of these scenarios will sometimes require the use of predictive techniques for estimating gas concentrations, over-pressure and thermal radiation levels and their effects. While these techniques are helpful in assessing the possible consequences of most major accidents, the resulting predictions are subject to substantial uncertainties which need to be taken into account when they are used. Having identified the various scenarios which could arise, the next stage is the consideration of appropriate counter-measures at the scene and elsewhere. There will need to be a rapid means of summoning help from those required to respond to the incident. It will be necessary to warn people who might be affected, but it should be recognised that this ‘warning’ might come after an explosion or a gas cloud has affected the people concerned. Plans for re-establishing containment may need to be developed. Personnel must be accounted for or searched for and, where necessary, casualty treatment must be initiated. Adequate arrangements for briefing the media must be in place: local radio can be most helpful in providing advice to the public. Having identified the scenarios and the counter-measures, the emergency plan can be prepared. It should be as flexible and as simple as possible and it must link readily with the plans of the other groups involved. It must be tested and modified if necessary. Regular joint training is essential and responses to notional toxic gas releases can be made more realistic by using time related displays of predicted gas concentrations on a computer generated map. However, due to the difficulty in assessing the release rate and the inherent uncertainties, any such predictions in a real incident should be used with care and only until field data are available.