Testing times for gas analysis

Demand for accurate and reliable emissions testing and monitoring systems that use quality specialty gases has never been greater as industries face ever-tightening environmental legislation. But what are gas suppliers doing to help meet this industrial challenge?

SPECIALITY gases are commonly used for emissions testing, where both pure gases and gas mixtures are used in gas analysis to take specific readings of gas components within samples taken from stationary sources. However, in recent years, such testing has become much more complex as more gas components need to be tested, often at lower concentrations than ever before.

These changes are being driven by evolving European anti-pollution legislation, which has put in place a raft of environmental directives in a bid to meet EU emissions reduction targets and help tackle climate change. This legislation specifies a wide range of environmental emissions – from carbon dioxide (CO2) and nitric oxide (NO) to volatile organic compounds (VOCs). In addition, a European quality standard for stack emissions monitoring systems - known as EN 14181 - is now widely in use offering guidance to ensure that emissions testing and monitoring is carried out accurately and in a consistent way.

But more change is on the way. At the end of 2007, the European Commission announced new proposals to toughen directives dealing with emissions such as dust, sulphur and nitrous oxides.  In addition, the Commission wants to simplify emissions legislation by bundling most of it together into a single Industrial Emissions directive. These new proposals have come following news that many European countries are failing to meet emissions reduction targets.

For all those involved in emissions testing, news of these changes is further confirmation that demand for accurate and reliable measurements is likely to continue to increase in the months and years ahead.

In a bid to ensure optimum accuracy and traceability, many laboratory analysts involved in emissions testing are seeking gas products that come with an assurance of quality. Most prefer to use certified gas calibration mixtures supplied by an ISO 17025 accredited laboratory. In fact, ISO 17025 certification is specified within EN 14181 and while not yet a requirement for industries other than waste incineration and large combustion plants, most industries have already adopted this standard.

To meet demand in this area, Air Products has recently extended its range of certified calibration gas mixtures produced at its European Specialty Gases Laboratory, which is accredited to ISO 17025 by the Spanish accreditation body, Entidad Nacional de Acreditacion (ENAC). This certification is recognised by UKAS in the UK, as well as by many other accreditation bodies, that operate in other parts of Europe, thanks to the multilateral agreement that applies under the European Cooperation for Accreditation.

This new capability means that for air emissions monitoring, it is now possible to produce certified calibration mixtures containing components like nitrogen and sulphur oxides and carbon monoxide at ultra low concentrations - as low as 400 ppb in air or in nitrogen - in order to achieve the most accurate calibration possible. For some industries, more accurate measurements could in some cases mean a reduced bill for environmental charges.

With such demanding analytical applications in mind, Air Products has also developed cylinder filling techniques and treatments helping to increase the accuracy and reliability of results further by ensuring that each gas mixture remains stable for longer. Improving the stability of gas mixtures means the uncertainty levels of the measurements taken are kept to a minimum.

These cylinder filling and treatment techniques draw on detailed knowledge about how individual gas components behave, at varying pressures and in different gas mixtures. For example, we know that such techniques are particularly helpful when mixtures contain reactive component gases like nitric oxide (NO), sulphur dioxide (SO2) or VOCs at low concentrations. By applying the right cylinder treatment and adjusting the way the compounds are weighed and added to the cylinder, the stability of the end product is significantly enhanced.

As gas mixtures become more complex and require lower concentrations, so the gas selection process itself is becoming more critical. Analysts need to be able to specify and source high quality gas mixtures 24/7 and they need to obtain quotes quickly too. 
As the drive for quality continues and the regulatory framework continues to tighten in emissions control, so many industries will need to work more closely with laboratory partners to achieve compliance and improve efficiency. Gas suppliers will continue to play an important role in supporting these industries by constantly looking for ways to improve accuracy and by providing certified calibration gas mixtures suited to the most demanding applications.

To trial Air Products’ gas mixture selector visit www.airproducts.co.uk/experismixtureselector.

By Lieve de Paepe. Lieve joined Air Products in 1990 after graduating as a chemical engineer from the University of Ghent, Belgium. Lieve is responsible for supporting the development of specialty gases for a wide range of industrial applications.