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Environmental monitoring

Controlled atmosphere test facility

Validating the performance of air quality monitoring sensors 

Our CATFAC facility provides a circulating stream of air containing controlled traceable concentrations of test gases in which instruments and devices for air quality measurement can be located. Instruments are placed within the system for exposure to the controlled environments for hours, days or weeks to simulate field behaviour.  

After exposure, either chemical analysis or thermal desorption with chromatographic methods are performed to determine diffusive sampling rates for pollutants including ammonia, nitrogen dioxide and benzene. This research is supporting the UK and European air quality (AQ) monitoring industry and has provided traceability for such measurements underpinning UK government legislation and EU AQ directives.  

NPL can evaluate accuracy of Ammonia (NH3) samplers  

NPL has developed new stable primary gas standards of NH3, and these have been employed in the CATFAC with differing commercial designs of diffusive and pumped sampling devices which are used routinely to detect ammonia. The study discovered that some samplers were displaying errors in reading of up to 40%. New diffusive sampling rates were determined to correct this. The results are being used by industry and have been published and included in the standard EN 17346 by CEN TC264 WG11.  

NPL can evaluate sampling rates of Nitrogen dioxide (NO2) Palmes diffusion tubes    

The CATFAC facility has been used to determine diffusive sampling rates of modified NO2 Palmes diffusion tubes (PDTs) which have been developed to reduce undesirable biases from wind turbulence. One design, developed in partnership with a Gradko Environmental, employs an amorphous polyethylene (PE) filter and has been implemented in Defra’s UK Urban NO2 Network (UUNN) This filter is enabling improved repeatability and reduced uncertainty for measurements of this pollutant. As a result, standard EN 16339 is being revised by CEN TC264 WG11 to accommodate the latest advances.  

This facility can provide an ideal solution for performing a matrix of comparative tests and rapid screening of sensor designs.

Please contact us to discuss details of your CATFAC testing requirements.

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