GASCO Calibration Gas 414-CO2 Mixture 300 PPM Carbon Monoxide, 10 PPM Hydrogen Sulfide, 2.5% Carbon Dioxide, 1.45% Methane (29% LEL),  (58% LEL Pentane Equivalent), 15% Oxygen, Balance Nitrogen, For Use with Any and All Gas Detectors, Calibration Certificate NIST, Made in the USA