GASCO 116L-411 Calibration Gas: Carbon Monoxide 100 PPM Carbon Monoxide, 25 PPM Hydrogen Sulfide, 0.35 % Pentane (25 % LEL), 19 % Oxygen, Balance Nitrogen contained in a 116L Liter GASCO Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA