Abstract. Automotive gas mixtures of carbon monoxide, carbon dioxide, oxygen and propane in nitrogen are used for the calibration of measurement equipment for automotive exhaust gases. This comparison involved four laboratories. Two have used their own gravimetric primary standards, one of them used standards prepared by an accredited laboratory and the other used their own gravimetric primary standards together with gravimetric primary standards prepared by other national laboratories.

CEM operated as the coordinating laboratory in this comparison. The selected primary gas mixtures for this comparison were individually prepared gravimetrically and thoroughly studied for their chemical composition and stability.

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