How to interpret the results from your screening or modelling exercise for Ammonia Emissions (GN 020)

What to do with the information from SCAIL 

The SCAIL tool will tell you what your development’s Process Contribution (PC) is at the sensitive sites within the screening distance. 

The Process Contribution is the amount of ammonia coming from your development. 

For ammonia it is expressed in micrograms per cubic metre (µg/m3). 

You will need to tell us what the PC from your development is and provide it as a percentage of the ammonia critical level. 

Once you have the results of the assessment 

If you answer yes to either of the following questions, then you will need to carry out detailed modelling.  

If you answer no to both questions then no further work is needed. Please provide SCAIL (or similar) output in pdf format with your application.  

• When you add your process contribution and the background level together is the critical level exceeded? 
• Are there any other sources of Ammonia that could affect the sensitive site? 

How to use the results from your detailed modelling 

We are using critical level as a standard to ensure the sensitive site is protected and to enable sustainable development. The following statements should help you decide on the next course of action.  

If the process contribution and background levels do not exceed the critical level and there are no other sources to consider then normally the application can proceed.

There will be occasions where the critical level is close to being reached. It is important to note that the critical level is not a target but a level that we want to avoid. Where the background is close to the critical level we may advise against the development even if the critical level is not exceeded. 

If the process contribution plus the background level reaches or exceeds the critical level then abatement must be used to reduce the process contribution to below 1% of the critical level, in order for the application to proceed. Assuming there are no other sources of ammonia to consider.

If your process contribution is below 1% of the critical level and there are no other sources of ammonia to consider, the application can proceed regardless of the background level. 

Information of common ammonia reduction techniques can be found on our Ammonia reduction techniques page.

If you are proposing the use of scrubbers please read ‘Ammonia scrubber design and use'.