Intercomparison of primary NO(2) calibration standards
The reference method for NO(2) measurement proposed by the EC directive (85/205/EEC) is the method of chemiluminescence according to ISO standard 7996. This norm includes a calibration procedure based on the permeation method (ISO standard 6349) which is the reference calibration method of the directive. Recent investigations on the reliability of the permeation method showed instability and abnormal reproducibility of the permeation rates of NO(2) tubes, questioning its implementation as primary standard. A systematic overestimation of the permeation method with respect to the Saltzman wet chemical method was also evident. These effects were attributed to the possible presence of impurities in the liquid NO(2). New developments in the Saltzman method and the static volumetric method are proving a valuable alternative to the reference calibration method. The German VDI recently proposed new versions of these calibration methods. According to the directive their compliance with the reference calibration method still required testing. The intercomparison between primary NO(2) calibration standards was designed to answer the following questions: (i) how reliable are the NO(2) permeation tubes used in EC monitoring networks? (ii) what is the origin of the instability observed in some permeation tubes? (iii) how well do other primary standards comply?
Bibliographic Reference: Paper presented: Measurement of Nitrogen-containing Compounds, Les Diableters (CH), June 29 - July 3, 1992
Availability: Available from (1) as Paper EN 36822 ORA
Record Number: 199211529 / Last updated on: 1994-11-29
Original language: en
Available languages: en