The Calibration Standard Gas Mixture for LPG are prepared by Gravimetric method as per ISO: 6142 and calibrated as per ISO: 6143:2001, Certified on % wt. basis as well as in mole % basis and should have trace ability to National/International Standard which is to be specified. The Certification accuracy is +/- 1 % or better.  The stability period of the Mixtures is minimum 12 months.