FACILITIES FOR THE TESTING OF GAS MONITORING INSTRUMENTS AT THE NATIONAL PHYSICAL LABORATORY

1 INTRODUCTION
The National Physical Laboratory (NPL) has developed facilities for the laboratory testing and calibration of gas monitoring instruments as part of the VAM (Valid Analytical Measurement) programme of the Department of Trade and Industry. This paper describes some of these facilities, including gas cells for testing open-path instruments and a laboratory which is dedicated to the testing of CEMs (Continuous Emission Monitors). The latter is UKAS accredited for a range of tests which include the laboratory test requirements of the MCERTSCertification Scheme. A comprehensive facility is also described which is being developed for the performance testing of pumped adsorption tubes and diffusion tubes, which are used increasingly for measurements of ambient air and occupational exposure.