Importance of Air Dispersion Modelling for Licensed Facilities in Ireland and the UK

An air dispersion model is used to determine the impact of stack or other air emissions on the local ambient air quality.  Environmental Efficiency uses AERMOD and other software to investigate this air modeling.

Air Dispersion Model: Investigating the impact of air emissions

Air emissions from stacks, bag filters, waste water treatment plant and other sources can cause health and nuisance problems not only in the locality but sometimes 10’s of kms away.  These air emissions (termed the process contribution), when added to the ambient air (termed the background contribution) may cause the EU air quality standard to be breached.  This may prevent the proposed development proceeding.

To determine whether the proposed development’s air emissions will cause a breach of the EU air quality standards requires a prediction of the process contribution at various distances from the development.  This air modeling prediction is evaluated for a range of wind directions and atmospheric conditions. The predicted process contribution is then added to the background contribution to determine the total concentration.  This total is then compared to the air quality standard.

Air Modelling: Use of screening models

Running an air dispersion model is time consuming as typically three years of meteorological data is used together with data regarding the topography of the area.  Environmental Efficiency’s initial approach is to run a screening model.  This will assume worst case weather conditions.  If the screening model predicts no adverse impact on air quality then regulators will accept that.  This results in a significant cost saving.

If the screening model indicated that local air quality is breached, then a full air dispersion model is required.  Environmental Efficiency use AERMOD to perform air modeling.  This program is the industry standard. Our staff includes certified AERMOD and CALPUFF modellers.

Stack Testing

Stack testing is a service provided by Environmental Efficiency; whereby we will monitor the air of an emission point like boilers or industrial processes. Visit our stack testing page now for more details.

What if the results are too high?

Where the results from an Air Dispersion model show high concentrations, the effect of increasing stack height, increasing gas velocity or other modifications intended to reduce concentrations can be investigated by our team.

What guidance is available?

The EPA Guidance Document AG4 is the key guidance document in Ireland for air dispersion modelling. In the UK the equivalent document is the Environmental Agency’s Air Dispersion Modelling Requirements.

Environmental Protection Agency (EPA)

In Ireland, the Environmental Protection Agency (EPA) requires licensed facilities to carry out air dispersion modelling as part of their licensing process. The modelling is used to assess the potential impacts of emissions on air quality and to determine if the facility’s emissions are within acceptable limits. The EPA provides guidance on the use of air dispersion modelling in the licensing process, including the use of approved models and the collection of input data.

Similarly, in the UK, the Environment Agency (EA) requires licensed facilities to undertake air dispersion modelling to assess the impact of their emissions on air quality. The modelling is used to determine if the facility’s emissions comply with the relevant regulations and to identify any measures that may be necessary to reduce emissions.

Air dispersion modelling typically involves the use of computer models to simulate the dispersion of pollutants emitted from a facility. The models take into account a range of factors, including the type and quantity of emissions, the location of the facility, and meteorological data such as wind speed and direction. The output from the modelling can be used to estimate the concentration of pollutants in the surrounding air and to assess the potential impact of emissions on human health and the environment.

Overall, air dispersion modelling is an important tool for assessing the impact of emissions from licensed facilities on air quality and human health in Ireland and the UK. By providing a quantitative assessment of the dispersion of pollutants, it can help to identify potential risks and inform decision-making about the management of emissions from industrial facilities.

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