Industrial Scientific Calibration Gas Mixture 1810-9159 Equivalent by GASCO Hydrogen Sulfide 25 PPM, Carbon Monoxide 100 PPM, Pentane 3500 PPM (25% LEL), Oxygen 18%, Balance Nitrogen in a 900 Liter Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection CGA 330, Calibration Certificate NIST, Made in the USA