The gas mixture in calibration gas cylinders is certified
to be prepared gravimetrically, using NIST traceable
weights. The lot number and nominal value of the
gas constituents in volume, percent by mass, PPM, or
volume is specified on the cylinder. Cylinder contains
Hydrogen Sulfide 20 PPM, Carbon Monoxide 60 PPM,
Pentane 58% LEL (1.45% Methane) , Oxygen 15%,
Nitrogen Balance.