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Frequently asked questions


For Mossmorran we continue to regulate robustly and this includes:

  • Working closely with the HSE as the Competent Authority under the Control of Major Accident Hazards Regulations to continue to assure ourselves that both operators are taking appropriate steps to manage any Major Accident risks.
  • Continuing to monitor noise and air quality across local communities.
  • Continuing to work with the companies to deliver flaring improvements in the shortest possible timeframe. We continue to be in regular contact with both companies to monitor progress.
  • Reviewing and following up on complaints. We encourage people to use our web reporting tool where possible.
  • Continuing to respond to any significant elevated flaring by deploying staff on the ground where appropriate. 

More information on the regulations for the Mossmorran Complex are available at How we regulate Mossmorran.

Details on our compliance and enforcement work, including our inspections, can be viewed at our Compliance and enforcement page.

The site is regulated by a number of organisations including the local authority, SEPA, and the Health and Safety Executive. We also consult with NHS Fife, Health Protection Scotland and Forth Ports in order to gain information and views to support our regulatory work.

More information about how we work together is available on our How we regulate Mossmorran page.


The flares are part of the safety system and are used to burn off gas that cannot be processed safely due to the volumes involved or the gas being off specification. This might be due to scheduled maintenance requiring the plant to be ‘gas free’ prior to entry; or, following an unplanned operational interruption. The flare systems include:

  • two 80 metre high flares at Shell FNGL;
  • one 100 metre high flare at ExxonMobil FEP;
  • two ground flares which are operated by Shell FNGL but used by both sites as required.

The number and type of flaring events varies year to year. These events can last just a few seconds and minutes to hours and days depending on the circumstances at the time. The primary reason for flaring is safety and events can be either planned or unplanned in nature. In years where there are more planned maintenance activities an increase in the number of flaring events can be expected.

To understand the frequency, type and duration of flaring events that occur, both operators at Mossmorran are required to provide an annual report to SEPA. 

This data is used as part of the regulatory controls applied by SEPA to both operators under their PPC permits. Flaring incidents must also be notified to SEPA and an incident report submitted (normally one to two pages in length) which SEPA then follows up directly with the relevant operator.

Under the Energy Act 1976 and Petroleum Act 1998, Shell are also required to have consents in place from the North Sea Transition Authority for flaring and venting of hydrocarbons.

The gases burnt in the flares are mainly methane, ethane, propane and ethylene, with smaller quantities of propylene, butylene, acetylene, benzene, toluene and hydrogen. Therefore, the flare plume will contain combustion products (principally carbon dioxide, carbon monoxide, nitrogen dioxide etc) and small quantities of unburnt hydrocarbons along with nitrogen and steam which are added to the flare to make it operate safely and efficiently.

ExxonMobil Chemical Limited at FEP and Shell UK at FNGL are permitted to flare for safety purposes. However, there are conditions in the PPC permits relating to flaring which aim to minimise community disturbance and pollution from flaring.

In general the visual and noise impact of flaring is minimised by using the ground flares; forward planning to ensure that any required flaring takes place mainly during daylight hours; and, minimising the amount of material to be flared. However when the ground flares are not available, or the flow-rates are too great (e.g. in certain start-up or shutdown operations), then the elevated flare is also used.

Smoky flaring can be minimised by the addition of steam to optimise combustion. However, excessive steam addition can give rise to noise nuisance and must therefore be carefully managed.

It is a condition of both operators’ PPC permits that they must not emit smoke exceeding a specified darkness of shade (Ringelmann Shade 2) from ground flares and elevated flares for longer than 15 minutes.

The Ringelmann chart is used to define dark smoke. The chart has five shades of grey with 0 being clear and 5 being black. Smoke is considered ‘dark’ if it is shade 2 or darker.

Any major flaring resulting in burning of hydrocarbon above five tonnes per hour for a period of 30 minutes also requires seven days prior notification to SEPA.

Any major flaring which is not notified in advance, requires the operator to follow the incident procedures in the PPC permit. This includes formal notification to SEPA without delay and a follow up investigation report within 14 days to confirm the causes of the flaring event, the environmental impact and measures to prevent a further flaring event due to similar causes.


SEPA submitted its report in July 2020. Upon receipt of the report, COPFS become responsible for the assessment and progression of the case and any enquiries about the report should be submitted directly. Contact details and further information can be found on COPFS' website.

Details on our compliance and enforcement work, including our inspections, can be viewed at our Compliance and enforcement page.

Air quality monitoring

The air quality section of our Mossmorran Hub has a comprehensive overview of the monitoring being undertaken by SEPA, monitoring results and our forward programme.

SEPA does not undertake any additional air quality monitoring during flaring events. Our forward air quality monitoring programme has been designed to provide data through-out the year and during all operational conditions at the plant.

Our latest air quality monitoring reports are available on our air quality monitoring page.

Air quality and health

Local authorities have a statutory duty to review and assess local air quality in their area against the air quality objectives for various pollutants (including benzene) that are in-place to protect human health. These air quality objectives are contained within the National Air Quality Strategy for England, Scotland, Wales and Northern Ireland which was last updated in 2007.

We have  a statutory responsibility to ensure that PPC regulated processes do not result in, or contribute to, an exceedance of relevant air quality objectives.

Air quality is typically assessed by a combination of modelling and monitoring.

A number of modelling studies have been undertaken, the latest being in 2019 by Wood Group on behalf of ExxonMobil FEP. In this case a computer model was used to predict the maximum ground level concentration of pollutants that could occur where members of the public are present as a result of emissions from FEP, based on a worst-case scenario (flaring rates tripled and flaring at this rate occurring 365 days of the year with black smoke). In addition to emissions from FEP, it also accounted for:

  • the emissions from the neighbouring Shell Fife FNGL Plant;
  • other non-industrial sources, such as roads and domestic emissions;
  • the presence of the wind turbines near to Mossmorran.

The computer model considered emissions of nitrogen dioxide, carbon monoxide, particulate matter, unburnt hydrocarbons, benzene, toluene, ethyl benzene and xylene and predicted that concentrations of all air pollutants emitted from FEP were well below air quality objectives.

This conclusion is consistent with previous modelling and ambient monitoring studies, and SEPA’s monitoring continues to show that levels of the pollutants measured are consistently below air quality standards.

We are currently satisfied that the emissions from the Mossmorran complex are not having a detrimental impact on air quality in the local communities. Modelling and monitoring studies have consistently shown that the concentrations of the pollutants assessed are currently well below the air quality objectives at local residential areas. This conclusion is backed up by the Mossmorran and Braefoot Bay Independent Air Monitoring Review Group.

In October 2019, NHS Fife published a summary of work carried out by or for NHS Fife public health department to investigate and assess health-related claims with respect to the Mossmorran plant in Fife. This report concluded that “there continues to be no evidence of significant negative impacts in terms of air quality or cancer incidence” but acknowledged that during the period assessed “it is clear that the degree of physical and psychological disturbance caused to people in the vicinity of Mossmorran has been considerable”.

The Air Quality in Scotland website has a considerable amount of information on Air Quality across Scotland including explanations on Air Quality Standards and the Daily Air Quality Index as well as monitoring results from Automatic Urban and Rural Network sites.

Fife Council's website has information relating to the Air Quality assessments they undertake, Air Quality management Areas and the Mossmorran and Braefoot Bay Community and safety Liaison Committee Expert Advisory group on Air Quality.


Subject to legal constraints, we will make noise assessments available in the Compliance and enforcement section. This will include SEPA noise assessments and noise reports submitted to SEPA by the Operators.

There is a condition in the Fife Ethylene Plant permit which requires the operator to ensure all appropriate preventative measures are taken against noise and vibration emissions through the application of Best Available Techniques and ensure that no significant pollution is caused. Our inspection and noise monitoring programmes are designed to assess compliance with this noise condition in the permit. 

Setting specific numeric noise limits at sensitive receptors (such as nearby housing) is not always practical, necessary or the best approach to assess compliance or the impact on the local community, particularly where there are other sources of noise, such as busy roads. It could be difficult to demonstrate non-compliance and take action if; for example, a noise just below the numerical noise limit continued for a long period or if the nature of the noise changed to make it more annoying. A numeric limit assumes the nature of the noise won’t change. 

Where it is practical to set a noise limit, a considerable amount of data is needed to understand the local noise environment and determine an enforceable limit.

SEPA is currently reviewing whether to set a specific noise limit at the Mossmorran complex.

We normally assess noise at or close to sensitive receptors near industrial sites. Monitoring normally takes place outside people’s homes, and the British Standard methodology is designed for this.

We currently assess noise from Mossmorran using British Standard 4142. This is based on a comparison between the sound which is being assessed and the background sound which would exist without it. The comparison takes into account the measured sound level, any character of the sound that might make it more annoying and the context in which the noise is heard.

We use this assessment, alongside additional information like the length of the event and the observations of staff in community locations during the event to determine the level of impact that has occurred. 

SEPA is in the process of auditing the consultant that has installed the noise monitoring equipment for ExxonMobil and is providing the data collection and processing service to them. This audit will ensure that their systems and procedures are appropriate and compliant with the relevant standards.

We will continue to check that these systems and procedures are followed to ensure that the assessments and data reported to us are correct.

We have two noise monitors currently deployed - one in Lochgelly and one on farmland closer to the plant.

The British Standard for assessing the impact of industrial noise (BS 4142) has been in operation for over 50 years – it is the approved method used by all UK environment agencies for characterising noise impact on communities close to industrial processes and is based on sound levels measured outside (rather than inside) residential properties.

They are effectively the same. Both continuously record sound levels through-out the period that they are deployed and periodically record sound files so that we can listen to the actual noise for review.

The continuous noise monitors provide 24-7 noise monitoring and allow us to get data on short events or capture data during the early stages of any event where the deployment of staff may take a short period of time.

However, they are in fixed locations and so, where possible, during significant flaring episodes SEPA noise assessors also carry out spot checks with battery powered noise monitors allowing flexibility in assessment location, this means we can dynamically target and assess the most affected areas.

The noise monitors that are continuously recording are set up in such a way that we can communicate with them remotely, and they are powered in such a way to ensure continuous data collection. Hand-held units used for spot checks during flaring events are battery charged and the data collected is downloaded direct to a computer on return from a field visit.