Medium Combustion Plant and Specified Generators – Pollution Prevention and Control

The medium combustion plant requirements of the PPC 2018 amendment regulations are designed to control emissions of sulphur dioxide (SO2), nitrogen oxides (NOx) and dust into the air from plants with a net rated thermal input of between 1 and 50 megawatts (MW), contributing to better air quality and reducing the potential risks to human health and the environment.

If you operate your own boiler, engine or generator (including back-up/stand by) for the production of heat or power you may be running a medium combustion plant (MCP), and it is likely you will have to apply for a permit from us or the NIEA if operated on a Part A or Part B installation to continue using it.

This page is designed to help you understand if the legislation is relevant to you and, if it is, what you have to do, when you have to do it by and how we can help you.

The process below will help you decide whether you need to apply. If you already know you need to apply please check the contents of this page to find information to help you do this.

1. Do you have a boiler, generator or engine burning any fuel which was put into operation before 20 Dec 2018?

• Yes – go to step 2.
• No – if your plant was put into operation after 20 December 2018 it should already have a Medium Combustion Plant permit. If you do not, contact us at

2. Does it have a capacity of 5 megawatts (MW) net rated thermal input or more but less than 50MW?

• Yes – go to step 3.
• The input is higher – you should already have a PPC permit. If not contact the NIEA
• The input is lower – if your plant is between 1 and 5MW you may need to register with us in the future. You have until 30 June 2028 to do this.
• I don’t know – contact us at

3. Does it have a capacity between 20MW and 50MW?

• Yes – you should already have a PPC permit. If notcontact the NIEA.
• No – go to step 4.
• I don’t know – contact us at

4. Does it fit one of the exclusions listed in the Directive (see text below)?

• Yes – this legislation does not apply to you.
• No – continue to step 5.
• Not sure – contact us at .

5. Is your existing medium combustion plant on a PPC permitted Part A or Part B installation?

• Yes – NIEA will already have sent you an information notice requiring you to provide information about the medium combustion plant at your installation. They will then vary your permit to include conditions relevant to the medium combustion plant at your installation. Details of the variation fee would have been provided with the information notice. If you have not received an Information Notice from NIEA by 31 May 2023 please contact the NIEA.
• No – continue to step 6.

6. You will need to apply to us for a permit to operate your medium combustion plant now.

• Find out how to apply for a PPC Part C permit for a medium combustion plant.

If you have more than one medium combustion plant on your site:

• When we speak about medium combustion plant we mean an individual boiler, generator or engine. If you have more than one plant on your site you need to think of them individually for the purposes of this flowchart/process.
• You can apply for all the medium combustion plant for your site on one application form if you operate them all – as long as the total capacity for the site is less than 50MW.

There are a number of exclusions detailed in Article 2(3) of the MCP Directive including:

• combustion plant used to propel a vehicle, ship or aircraft;
• turbines and engines used on offshore platforms;
• some driers;
• thermal oxidisers.

There are a number of exemptions listed in Article 6 of the MCP Directive. Plants subject to these exemptions will still need to be permitted but are exempt (sometimes on a time-limited basis) from compliance with ELVs. These include:

• plant operating under a certain number of hours (NB on islands):
• use of biomass,
• plant serving a public District Heating Network.

All exclusions and exemptions have been adopted in the NI regulations. Please use the links to the detail in the Directive to ensure you have checked the full list. If you are still unsure, please contact us at

All the UK Regulators are working together to ensure consistent regulation of medium combustion plant and have agreed definitions and guidance to apply across the United Kingdom.
Follow this link to view frequently asked questions about medium combustion plant.