1987 Volume 22 Issue 6 Pages 460-472
In U.S.A., as developing programs of the Air Pollution, it was controlled by thelaw of the Clean Air Act. And the Mobile Source Air Pollution Controll program has developed a system of primary gas standards which permits commercial gas blend to be named within 2% of true values and traceability relationship of each gas to NBS's SRM.
And then the measuring method of CO, NOx and HC in motor vehicles exhaust gases was specified by the regulation of the control of Air Pollution from new motor vehicles and new motor vehicle engines.
According to it regulations, it was enacted that calibration gases shall be traceability to within 1% of NBS gas standards or other gas standards which have been approved by the administrator, and more, span gases shall be accurate within 2% of true concentration, where true concentration refers to NBS gas standards or other gas standards which have been approved by the administrator.
In Japan, the traceability of reference gases have been established with the inspection system of them by CITI under the guidance of MITI (ministry of International Trade and Industry).
Therefore, in order to make the international agreement of concentration of reference gases, we performed the round robin test between NBS, EPA, BOC, VSL and AL about the each concentration of samples of some reference standard gases which were prepared by gravimetric method.
It is concluded that the reference gases of the participating countries agreed well in the concentration and most of their difference between the countries were within 1% except the following data; 5 ppm CO-N, (NBS and EPA), 1200 ppm C3H8-N2 (NBS), 5 ppm and 20 ppm NO-N2 (AL, CITI) and 500 ppm, 100 ppm and 50 ppm 5O3-N2 (BOC, NBS).
