Statutory guidance

Generic risk assessment for standard rules set number SR2018 No 1

Updated 26 February 2026

Applies to England

SR2018 number 1: Specified Generators, Tranche B low risk, base load operation between 0 to less than or equal to 5 MWth.

The Environment Agency produces the generic risk assessments for all standard rules permits. These list the potential risks and specify the measures required, to manage them. The list of specified measures is not intended to be exhaustive or comprehensive and additional appropriate measures may be required to manage potential risks.

Applicants should check the risk assessments to understand:

• the potential risks of MCP under this standard rule set
• if your proposed activity has the same risks as MCP and whether you can apply for the standard rules permit
• how to manage the risk effectively

Each risk comprises:

• information about the source, pathway and receptor and the potential harm to that receptor
• an assessment of the level of risk and justification of that assessment
• actions for managing the risk (through permitting) and a residual risk rating after managing it

Risk management involves breaking or limiting the source-pathway-receptor linkage to reduce the risk. If the Environment Agency set minimum distances they explain the basis of the distances, for example by modelling.

The Environment Agency control the residual risk (after risk management) when they assess compliance.

If you need to check the meaning of any terms used (in the context of this risk assessment), see the explanation of terms in this document.

This generic risk assessment is based on the following parameters which define the scope of the permit and associated rules.

Parameter 1

Total aggregated net thermal input of all combustion plant is less than or equal to 5 MWth.

Parameter 2

The stack height shall be no less than 3 meters and must be vertical and unimpeded by cowls or caps.

Parameter 3

Minimum distance from any point source emission to a sensitive human receptor is 100 or 150 meters, depending on the total aggregated thermal capacity.

Parameter 4

The site must be a minimum distance from a protected habitat. The distances are specified in the permit and will depend on the type of fuel and total aggregated net thermal input capacity of the combustion plant

Parameter 5

The background NO₂ concentration at sensitive human receptor must be less than 31 µg/m³.

Parameter 6

Specified Generators shall not be located in an AQMA declared for NO₂.

1. Risk to local human population

1.1 Releases of oxides of nitrogen (NOx)

NOx gases travel through the air and can be inhaled.

Where the plant is in an Air Quality Management Area and there is a relevant published plan enacted through the Air Quality Standards Regulations 2010 a bespoke permit will be required.

We have assessed the potential harm to human health as follows:

• respiratory irritation
• illness

Assessment of risk

The Environment Agency has assessed the:

• likelihood of the hazard affecting the receptor to be low
• overall severity of potential consequence to be medium
• overall risk rating to be medium

The reasons for giving the activity this rating is because there is a potential for exposure to:

• anyone living close to the site
• members of the public at locations to which they have access to an could be regularly exposed

Managing the risk

The following measures will normally manage the risk:

• activities shall be managed and operated in accordance with a management system (including inspection and maintenance of equipment, including engine management systems)
• point source emissions to air with emission limits for NOx
• the activities shall be carried out where the NO₂ background is less than 31 µg/m³, ensuring the Environmental Standard to protect human health is not exceeded 150 meters from the stack

Taking these actions will normally control the risk so that it can be rated as ‘medium’.

2. Risk to protected habitat sites

Protected habitat sites include:

• Special Areas of Conservation
• Special Protection Areas
• Ramsar wetland areas
• Marine Conversation Zones
• Sites of Special Scientific Interest

Protected habitat sites can be at risk from any source and by any pathway. However, the main risk is from NOx. Minimum distance parameters specified in the permit do not allow operations in close proximity to protected habitat sites.

The risk of harm to protected habitat sites includes (but is not limited to):

• toxic contamination
• nutrient enrichment
• disturbance

Assessment of risk

The Environment Agency has assessed the:

• likelihood of the hazard affecting the receptor to be low
• overall severity of potential consequence to be medium
• overall risk rating to be low

The reasons for giving the activity this rating is because:

• emissions to air may cause harm to and deterioration of protected habitat sites.

Managing the risk

The following measures will normally manage the risk:

• activities shall be managed and operated in accordance with a management system (including inspection and maintenance of equipment, including engine management systems)
• point source emissions to air with emission limits for NOx

Taking these actions will normally control the risk so that it can be rated as ‘low’.

3. Explanation of terms

Likelihood of exposure

This is the likelihood of the receptors being exposed to the hazard. The meaning of the definitions are:

• high – exposure is probable – direct exposure is likely with no or few barriers between the hazard source and the receptor
• medium – exposure is fairly probable – feasible exposure is possible as the barriers to exposure are less controllable
• low – exposure is unlikely – several barriers exist between the hazard source and receptor to reduce exposure
• very low – exposure is very unlikely – effective, multiple barriers are in place to reduce exposure

Overall magnitude of potential consequence

This is the severity of the consequence if the hazard is realised and may cause actual or potential harm.

This will have a high, medium, low or very low rating using attributes and scaling to consider ‘harm’.

Risk rating

The Environment Agency determines the risk rating by combining the likelihood of exposure with the magnitude of the potential consequences.

The Environment Agency assesses these ratings to be:

• high risk – requires additional assessment and active management
• medium risk – requires additional assessment and may need active management or monitoring (or both)
• low and very low risks – will require a periodic review