The HCl Standard Reference Method (SRM, EN 1911), which is legislatively required for measuring industrial emissions, is unable to meet uncertainty requirements being brought in via Best Available Techniques (BAT) Conclusions documents (which set permit conditions for regulated industrial processes). This puts at risk the new regulatory framework and the ability of national regulators to carry out enforcement interventions. The project will address these issues by recommending uncertainty requirements for extending the application of the SRM with an associated underpinning evidence base; and providing an evidence base of the performance of portable optical technologies with a view to replace the SRM in the longer term. Limiting emissions of HCl from industrial processes is critical, as this is acutely toxic and impacts on far more ecosystems than previously thought . The HCl emission limit for industrial processes regulated under the Industrial Emissions Directive  used to be 10 mg.m-3. However, BAT Conclusions documents the EU is bringing in increasingly stringent emissions limits impacting a range of industries (e.g. 2-6 mg.m-3 for waste incineration, <1-3 mg.m-3 for iron and steel production , 3-12 mg.m-3 for power stations ). The legislatively required SRM for monitoring HCl emissions is described in EN 1911  and is based on extracting stack gas through deionised water in glass impingers before off-line analysis, generally by ion chromatography. It is a requirement that the emission measurement meets an uncertainty of 30 % (k = 2) of the emission limit, but this is not possible at limits below 10 mg.m-3 . The method uncertainty is subtracted from the reported emission prior to comparison to the emission limit, thus ensuring any breach is ‘beyond reasonable doubt’ (i.e. 95 % confidence) and that there is justification for national regulator enforcement intervention. Hence, if the method uncertainty is unclear then enforcement becomes untenable. To address these issues there have been three key needs identified, from which the project’s objectives derived: CEN/TC 264 ‘Air Quality’ have listed in their future priority work document  the need for “assessment of current SRM to meet stricter limit values”; CEN/TC 264 ‘Task Force Emissions – who provide recommendations to the European Commission – have stated that a regulatory guidance document is needed on, “…stationary source emissions providing information on the field of application of the methods (measurement range, validation range, uncertainty, etc.)”; CEN/TC 264 in  have identified the need for work on “automated methods for measuring emissions”. This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. References Hydrochloric Acid: An Overlooked Driver of Environmental Change. Chris D. Evans, Don T. Monteith, David Fowler, J. Neil Cape, and Susan Brayshaw. Environmental Science & Technology, 2011 45 (5), 1887-1894. DOI: 10.1021/es103574u. Directive 2010/75/EU of the European Parliament and of the Council of 24 November 2010 on industrial emissions (integrated pollution prevention and control). OJ EU L334: 17-119. Best Available Techniques (BAT) Reference Document on Waste Incineration (2017). Joint Research Centre, draft 1, May. 2012/135/EU: Commission Implementing Decision of 28 February 2012 Establishing the Best Available Techniques (BAT) Conclusions under Directive 2010/75/EU of the European Parliament and of the Council on Industrial Emissions for Iron and Steel Production. OJ EU L70: 63. Commission Implementing Decision (EU) 2017/1442 of 31 July 2017 Establishing Best Available Techniques (BAT) Conclusions, under Directive 2010/75/EU of the European Parliament and of the Council, for Large Combustion Plants. OJ EU L212: 1. EN 1911:2010, Stationary Source Emissions — Determination of Mass Concentration of Gaseous Chlorides Expressed as HCl — Standard Reference Method. Study on AMS and SRM Performances and their Impact on the Feasibility of Lowering ELVs for air Emissions in the Context of the BREFs and BATs Revision and of BAT AELs Elaboration According to the IED. European Suppliers of Waste-to-Energy Technology (ESWET), Confederation of European Waste-to-Energy Plants (CEWEP), European Federation of Waste Management and Environmental Services (FEAD). 22nd July 2016. Future Work Items / Activities of CEN/TC 264. CEN/TC 264 N2204, 30th March 2014. CEN Task Force Emissions, Decision 3, Düsseldorf, 10th & 11th January 2018. CEN/TC 264/TFE/N 84.