This project will deliver the pre-normative work without which full implementation of the EU’s Industrial Emissions Directive will not be possible negating some of the health and the environmental benefits it is designed to deliver. Furthermore, this project will support CEN/TC 264 “Air Quality” in terms of laying the platform necessary to develop a new Reference Method for regulatory monitoring of Sulfur Dioxide (SO2) emissions from industrial processes.



There is a need to take continued steps to reduce pollution from industrial process plants to realise both health and associated economic benefits. The recent Industrial Emissions Directive (IED – 2010/75/EU) is bringing in increasingly stringent emission limits for a range of pollutants to meet these aims. The European Commission estimates that if this directive can be successfully enforced it will result in a reduction in premature deaths / years of life lost in Europe of 13,000 and 125,000, respectively, and realise associated cost savings of €7 – 28 billion per annum (COM(2007, 843 final)). There are also environmental drivers to reducing pollution as, for example, it was recently shown that the risk of SO2 acidification of water and soil has been underestimated (www.eea.europa.eu/highlights/europe-still-playing-catch-up ).

The seven prior directives that the IED has replaced were enforced through a series of Standard Reference Methods (SRMs) produced by CEN under mandate from the European Commission. These methods being either directly passed into, or referred to, in member state legislation, i.e. such CEN standards have special standing. With the decreased emission limits coming into force under the IED it is becoming clear that these SRMs may no longer be fit for purpose on all industrial processes. This issue has been formerly recognised by CEN/TC 264 who have highlighted the following future needs: “identify new monitoring requirements of the IED”; “assessment of current SRM to meet stricter limit values”; and “automated methods for measuring emissions” (N2204 Future Work Items of CEN/TC 264).

With respect to the current SRM for SO2 (EN 14791) the original mandated validation work found an associated uncertainty ±1.7 mg.m-3 (95 % confidence), whereas, for example, for LNG combustion gas processes the IED now requires ±1.0 mg.m-3 (95 % confidence). Ultimately, such issues potentially compromise the enforcement of emission limits reducing the health and economic benefits described above whilst also impacting on the accuracy of the European Pollutant Release and Transfer Register, and commitments under the UNECE Convention on Long Range Transboundary Air Pollution (CLRTAP).



The current SRM for SO2 involves extracting industrial emissions and stack gas and passing it through a series of glass impingers filled with H2O2(aq) in which the SO2 is dissolved as sulphate. Off-line analysis of each sample performed in a chemistry laboratory then gives a sulphate concentration, which can be related back to the in-stack concentration. Hence, the SRM is based on ‘unconditioned sampling’ as there is no need to remove water vapour from the extracted stack gas. Many in the community wish to move towards using direct analysis instrumental techniques (e.g. non-dispersive infrared: NDIR) in order to realise the uncertainty and sensitivity requirements needed for enforcing increasingly stringent emission limits. However, such techniques rely on “conditioned sampling” and there is as yet insufficient evidence that the various conditioned sampling approaches proposed are able to transfer extracted stack gas streams to the analytical instrument without physical and chemical changes occurring. If the community is to move towards such instrumental techniques for SO2 it must first be demonstrated that conditioned sampling can be carried out compliant with current and future uncertainty requirements.