1810-2242 Industrial Scientific Calibration Gas Mixture Equivalent by GASCO 2.5% Methane, 25 ppm Hydrogen Sulfide, 100 ppm Carbon Monoxide, 19% Oxygen, Balance Nitrogen, contained in a 58 Liter Disposable Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder Connection C-10, Calibration Certificate NIST, Made in the USA