Air quality monitoring

SEPA Mossmorran Air Quality Network 

SEPA has been monitoring air quality in community locations surrounding the Mossmorran complex since August 2019. To date, our monitoring has shown no breaches of the air quality objectives, but we continue to monitor as it is clear in hearing from the community that there are ongoing concerns about air quality in the area. 

SEPA currently operates monitoring equipment at locations around the complex to assess long-term air quality conditions. 

Access the SEPA Monitoring Air Quality Network 


What SEPA and our partners do 

Our role in regulating facilities like the Fife Ethylene Plant is to protect the environment and human health. To do that we work with our public partners, including Fife Council and NHS Fife. 

Air quality objectives for various pollutants are set out in legislation to protect human health. In most cases the domestic air quality objectives for Scotland are the same as the limit values for the European Union (EU) Ambient Air Quality Directive. 

The EU air quality limit values continue to apply for industrial activities regulated under the Pollution Prevention and Control (PPC) regulations. SEPA has a statutory responsibility to ensure that regulated processes do not result in, or contribute to, an exceedance of these air quality limit values.

Local authorities have a statutory duty to review and assess local air quality in their area and work towards meeting the Scottish air quality objectives, and air quality assessments are carried out annually by Fife Council (see Air quality | Fife Council). 

NHS Fife is responsible for the protection and the improvement of its population’s health. 

We meet regularly with our partners, share the results of our air quality monitoring and keep them informed of any areas of interest around our regulation of the sites.  

This supports Fife Council local air quality reviews and, combined with sharing information on community health concerns, allows NHS Fife to assess and report when they consider appropriate (e.g. report on the health impacts of flaring). 

Where we monitor and what we monitor for

In response to community concerns SEPA has increased both the number of potential pollutants we measure and the geographic coverage of our air quality network. We have also developed an online tool that will enable you to see the air quality at each air quality monitoring analyser in nearly real time, whilst also being able to view historic data over recent months. 

Our new monitoring approach consists of one monitoring station with reference analysers at Auchtertool which is complemented by a network of indicative analysers (AQMesh analysers) deployed in local communities around the Mossmorran complex. This gives a clearer understanding of air quality in the whole Mossmorran area. 

The reference station has been placed in Auchtertool as it is the most suitable (situated in a local community, access to a power supply, easily accessible for maintenance), and closest location in a downwind direction from the Mossmorran complex. This station will provide high quality data that can be directly compared to the Scottish air quality standards and objectives. 

The AQMesh analysers are lamp post mounted multi-pollutant devices which will provide indicative data for the wider communities around the Mossmorran complex.

These analysers are easier to locate than the reference analysers due to their size and power requirements and can be installed in more accessible locations. They are useful in assessing short-term trends in pollutants; provide greater geographical coverage; and monitor for a wider range of pollutants including nitrogen dioxide, ground-level ozone, and particulate matter. 

An indicative AQMesh analyser is co-located with the reference monitoring station which allows results from the different types of analysers to be compared and assists with quality control. 

Map of Fife showing the position of SEPA's air quality analysers. There is a written list on this page that explains where these are.

Our reference analyser in Auchtertool monitors PM2.5 and PM10 using beta attenuation, and nitrogen dioxide using chemiluminescence. 

Our AQMesh analysers are positioned in community locations in:  

  • Aberdour; 
  • Auchtertool; 
  • Burntisland; 
  • Cardenden; 
  • Coaledge; 
  • Cowdenbeath; 
  • Kirkcaldy; 
  • Lochgelly. 

They monitor PM2.5 and PM10 using a light scattering optical particle counter and have electrochemical sensors to monitor nitrogen dioxide and other pollutants. 

Why we selected these locations 

The sites provide air quality information to the local communities around the Mossmorran complex and were selected and installed with support from Fife Council. 

The reference monitoring station was sited in Auchtertool as this is the closest community that is downwind of the prevailing wind direction from the Mossmorran complex.

The AQMesh analyser sites were installed on lamp posts with a suitable power supply. 

Why we selected these pollutants 

We are monitoring for pollutants that are either expected to be released in a significant quantity from the Mossmorran complex (as well as being released by various other sources in the area such as vehicle emissions and domestic sources) or those which were highlighted as a concern by the community.

We are not monitoring for species which are released at levels that are significantly below permitted release levels (e.g. sulphur dioxide, where stack emission test results are below the emission limit values, see the annual data returns page) 

Nitrogen dioxide (NO2) - This gas is produced by the reaction of oxygen and nitrogen during combustion. It is emitted from the combustion plants at Mossmorran as well as domestic combustion appliances and vehicle emissions.

NO2 may have adverse effects on the health of the respiratory system. It can irritate the airways and lower resistance to respiratory infections such as influenza. NO2 (and other nitrogen oxides) is also a precursor pollutant leading to the formation of ground-level ozone which can have health and environmental impacts. 

Particulate matter (PM) is the term used to describe solid or liquid particles suspended in the atmosphere. Particle size affects how deep a particle can penetrate into the lungs and circulatory system and be absorbed.

Particles can be generated mechanically (e.g. dust from vehicle tyres driving over roads), through combustion (e.g. burning wood or fuel) or through chemical reactions. Particles may also be made up of, or carry, substances which can affect health.  

  • PM10: This is particulate matter with a diameter of less than 10 µm (micrometres). PM10 are defined by international convention as being able to be deposited in the lung. Because it has the potential to cause effects on health, it is regulated in the UK and must meet a certain level.

    There are many sources, including road traffic, agriculture, industry, and personal or household activities (e.g. domestic wood-burning, cooking). 

  • PM2.5: This is particulate matter with a diameter of less than 2.5 µm. These particles can penetrate even deeper into the lung than PM10. This is also sometimes called ‘fine particulate matter’ and has been associated with various health impacts, especially with regards to lung and heart health.

    Fine particles can cause inflammation and heart and lung diseases, and impair lung development in children. In addition, fine particles may carry surface-absorbed carcinogenic compounds into the lungs.

    There are many sources, including road traffic, agriculture, industry and personal activities. 

We are also now monitoring for ground level ozone.

This pollutant has been reviewed by the Mossmorran and Braefoot Bay Independent Air Quality Expert Advisory Group, which concluded that:

“it is unlikely that emissions of NOx and VOCs arising from the operations at the Mossmorran plants and the Braefoot Bay terminal facilities would contribute to formation of ground level ozone in the local area. Rather, ground level ozone formation is more likely to be related to emissions from areas further away.”

However, it was clear from talking to the community that there was a request for more information about ground level ozone levels in the area. 

Ground level ozone is not emitted directly from any man-made source in any significant quantities. In the lower atmosphere, ozone is primarily formed by a complicated series of chemical reactions initiated by sunlight.

These reactions can be summarised as the sunlight-initiated oxidation of VOCs in the presence of nitrogen oxides (NOx). The chemical reactions do not take place instantaneously, but can take hours or days, therefore ground level ozone measured at a particular location may have arisen from VOC and NOx emissions many hundreds or even thousands of miles away.

Ground level ozone irritates the respiratory system, exacerbating the symptoms of those people suffering from asthma and lung diseases. 

Access the SEPA Monitoring Air Quality Network

Frequently Asked Questions 

A selection of frequently asked questions about air quality are provided below – if you have any additional questions that are not covered below please get in touch using our contact form.

Our broader Mossmorran frequently asked questions are also available.

Changes to monitoring

Why did SEPA decide to change the way it monitors air quality around Mossmorran? 

In 2019 we confirmed that our air quality monitoring around the Mossmorran Complex would continue throughout the period of investment and the installation of new flare tips and ground flares. At the same time, we committed to working with partner agencies with air quality responsibilities to assess future requirements. 

In September 2021, we held four community engagement sessions in partnership with Fife Council and the Health and Safety Executive to listen to the needs of the community. We used the feedback to inform our review of the monitoring we undertake and how we share the results of that monitoring with the local community. 

To date, our monitoring has shown no breaches of the air quality objectives, but it was clear in hearing from the community that there continues to be a concern about air quality in the area. The community asked for: 

  • Permanent monitoring of air quality in the communities around Mossmorran. 
  • Simple, easy to understand and timely data, with the ability to get more detail if required. 

How has your monitoring changed? 

We have reviewed how we will monitor air quality and, taking the feedback from communities into account, we have made changes to how we monitor  and how we make information available in a way that will hopefully provide greater reassurance to local communities. We have implemented a new monitoring plan that: 

  • changed the monitoring locations; 
  • increased the number of monitoring points; 
  • increased the range of air pollutants that we measure. 

The new monitoring enables us to offer improved ways of presenting data on the levels of the pollutants measured, including near to real time data provision. 


What is the difference between the Reference Analysers and the AQMesh analysers? 

Reference analysers are complex instruments which require housing in a temperature-controlled environment and need frequent maintenance and quality control checks to allow high quality data to be provided. They undergo a rigorous assessment and are accredited for air quality monitoring purposes. Data obtained from reference analysers are deemed “provisional” until a full quality control assessment can be undertaken. This is usually done annually. Whilst data can be provided in near to real time, this data will be provisional. 

More information on data verification and ratification can be found on the Air Quality in Scotland website.

The AQMesh analysers do not require such rigorous housing, are small - and therefore much easier to deploy - and do not have the same level of maintenance and quality control requirements. They can readily host several sensors in a single unit. This allows much greater geographic coverage as well as allowing a wider range of pollutants to be assessed. The data can be provided in near to real time. 

The data from the AQMesh analysers are not able to match the quality of the data from the reference analysers, however, with careful quality control and calibration they are a powerful tool when used in combination. 

How do results from the reference analysers and the AQMesh analysers compare? 

The reference analysers located at Auchertool are certified and run to a high standard which allows for official comparison with air quality standards. The AQMesh analysers are indicative, and the results can only be treated as such, allowing for short term trend analysis. We have located one AQMesh analyser in the same location as the reference analysers so that the results from the two set ups can be compared.  

The geographic coverage of the AQMesh analysers allows comparison in communities all around the Mossmorran complex, giving a greater understanding of the overall air quality in the area.  

Technical specifications of the air quality analysers


Reference analysers sited at Auchtertool 

Chemiluminescence NO/NO2/NOX

  • Analyser Manufacturer’s specifications: T200 
  • MCERTS Continuous Ambient Air Monitoring System certification - MC05006812 

BAM1020 PM2.5 Analyser: 

  • Manufacturer’s specifications: BAM 1020 
  • MCERTS Continuous Ambient Air Monitoring System & MCERTS for UK Particulate Matter: MC13023704 

BAM1020 PM10 Analyser: 

  • Manufacturer’s specifications: BAM 1020  
  • MCERTS Continuous Ambient Air Monitoring System & MCERTS for UK Particulate Matter: MC14025403 


I’m seeing a higher concentration than normal reported from one of the air monitoring analysers – what might be causing this?  

Short term elevated levels of some pollutants, especially PM10 and PM2.5, can be expected due to local activities such as traffic; agricultural activities (ploughing, harvesting, etc); domestic sources such as solid fuel burners or bonfires and transboundary air pollution episodes. 

It is important to note that due to the nature of the AQMesh analysers there may be occasions when high concentrations are displayed for pollutants which are due to circumstances other than pollution. This can happen due to electrical interference, weather conditions or sensor failures. 

All the near real time data is provisional and should be treated with caution as it may change once verified. This is done at least annually. 

I’m seeing a negative concentration being reported from one of the AQMesh analysers – what does this mean? 

At very low air pollution concentrations, where the air is very clean, the measurements may on occasion fall below zero. This can occur for a number of reasons, including instrument drift.  

There is a lower limit to which air pollutants can be measured reliably. Generally, a negative reading, if not indicative of a fault with the instrument, will mean that there are very low levels of air pollution. 

The SEPA Monitoring Air Quality Network presents real time data, but you haven’t indicated if the data is below or above the air quality standard, why not? 

Air Quality Objectives are presented as an air quality concentration (or standard) which can only be exceeded a certain number of times per year. 

Air quality standards are calculated as an average of a series of measurements collected over a time period. This time period varies depending on the pollutant and the standard. 

As we are presenting hourly-averaged real time data we are not displaying these in direct comparison to the air quality standards, which for most pollutants are averaged over longer than one hour periods. 

As an example, for PM10 we are presenting hourly-averaged real time data, but there are two air quality standards - one based on averaging all the results collected over a 24-hour period and a second based on averaging all the results collected over a year. 

Short term results may go above the numerical value of an air quality standard, but this should not cause concern. For example, elevated levels of particulate matter might occur if a diesel vehicle idles with its engine running close to one of our analysers. These standards are set as averages over longer periods to take account of short-term elevations in air pollutants. 

Air quality objectives are the number of exceedances of an air quality standard permitted during a measurement year. As an example, for NO2 the 1 hour standard is not to be exceeded more than 18 times a year. See Air Quality Scotland for more details. 

As we are presenting real time data we cannot compare against the air quality objectives which is judged against a count of the number of exceedances of the standard. 

I am seeing a regular pattern in the data, what does this mean?  

Nitrogen dioxide and PM10 and PM2.5 often show a diurnal pattern (that is a pattern over a 24-hour period). An example that can be observed in many locations is a peak in NO2 levels from vehicle exhausts during the main morning and evening commuting times. Ozone is dependent on sunlight levels and will therefore display a varying pattern based on levels of sunlight. 

To help you assess the health impacts of the air quality around you we have used a simplified form of the Daily Air Quality Index (DAQI) which has been applied to particulate and NO2 levels. This provides an immediate indicative assessment against agreed criteria to determine if these pollutants are at levels that may cause health impacts and provides health messages to at-risk people and the general population as a guide. 

We will be producing annual summary reports to review longer term data. The monitors have recently been deployed, therefore there is currently no directly comparable historical data at these sites. 

Longer term data and statistics for air quality monitoring sites operated by Defra, the Scottish Government and Local Authorities, which have been running for a longer period, are available at the Air Quality in Scotland website. The site also contains long-term trend graphs for NO2, PM10, PM2.5 and ozone from selected monitoring sites: Trends summary ( 

Why is there missing data?

There are three main reasons why there might be missing data.

  • We are reliant on remote communications to our analysers and these can fail on occasions. This type of issue should be short term, and the analysers will continue to collect data that we can subsequently upload into the Mossmorran Air Quality Network.
  • If an analyser breaks down we will have data gaps. We will seek to repair or replace the broken analyser as soon as we are able, but this might take several days depending on the issue. This will remain as a data gap once the unit is operational again.
  • If there is a power outage to any of our analysers they will stop working and we will have no data available.

Interpreting the data

How do I put the air quality data you are providing into a real-world context and understand what it means for me? 

To help you put into context what the data shared on this site might mean, we have provided a simplified form of the Daily Air Quality Index (DAQI).  

More information on the DAQI is provided on the Air Quality in Scotland website including advice on how to use the DAQI. 

Where can I get more information on the pollutants that are emitted from the Mossmorran Complex and the levels at which they are released? 

The results from monitoring of pollutants emitted from process stacks, undertaken by the Operators and independently on behalf of SEPA, can be found on the Mossmorran Complex annual data returns page of the Mossmorran Hub. These reports also contain a comparison of the measured results against any emission limit values set in the Pollution Prevention and Control permit for the relevant site. 

The Scottish Pollutant Release Inventory (SPRI) is a Pollutant Release and Transfer Register (PRTR) and has the primary purpose of making publicly available officially reported annual releases of specified pollutants to air and water from SEPA-regulated industrial facilities. It also provides information on off-site transfers of waste and wastewater from these facilities. 

The SPRI data is collected, quality assured and made public under the requirements of Freedom of Information and can be compared with PRTR information from other countries (the SPRI data also forms part of the wider UK-PRTR). SPRI datasets from 2002 to the present year (except 2003) are available and reported annually. 

Monitoring during flaring

What air quality monitoring does SEPA undertake around Mossmorran during flaring events. 

SEPA does not undertake any additional air quality monitoring during flaring events. Our air quality monitoring programme has been designed to provide data throughout the year and during all operational conditions at the plant. See the “Where we monitor and for what” section above for a comprehensive overview of the monitoring being undertaken by SEPA and monitoring results. 

Will the monitoring stations detect any emissions during flaring? 

There is a ring of monitors around the site, to allow for differing wind directions. Any significant impacts on air quality at the monitoring locations should be detected. However, all monitoring evidence to date has shown no perceptible impact on air quality from flaring in the communities around the Mossmorran complex. 

As discussed in the question “I’m seeing a higher concentration than normal reported from one of the air monitoring analysers – what might be causing this?”, higher than normal levels of pollutants could be due to a range of reasons, not necessarily related to flaring events. If air quality is affected by any activity, including flaring, then it should be detectable in a downwind location.  

Data from the Auchencorth Moss – rural background site is also provided alongside the SEPA monitoring data to show wider air pollution events, such as in the case of transboundary events across the region or Scotland as a whole. 

Air quality monitoring reports

Prior to the launch of the SEPA Mossmorran Air Quality Network, air quality monitoring reports were published by SEPA. You can view these on our archive page.

Further information on air quality 

Further information on air quality in Fife can be found at: Air quality | Fife Council. 

SEPA’s monitoring is robustly reviewed by the Mossmorran and Braefoot Bay Community and Safety Liaison Committee Expert Advisory Group on Air Quality (previously the Mossmorran and Braefoot Bay Independent Air Quality Monitoring Review Group), which includes independent technical expertise from the Institute of Occupational Medicine (who audited our data and data handling processes). Further information can be found at Mossmorran and Braefoot Bay | Fife Council. 

The Air Quality in Scotland website contains a lot of useful information on air quality and provides access to the wider Scottish air quality network. It also provides further information on the air pollutants which are being measured by this network, including any relevant air quality standards and objectives.