GASCO Calibration Gas Equivalent for Portagas 90095023 25 PPM H2S, 50 PPM CO, 1.62% CH4, 18% O2 Balance Nitrogen contained in a 10 Liter Aluminum Cylinder, For Use with Any and All Gas Detectors, Cylinder connection Built in Aerosol Trigger, Calibration Certificate NIST, Made in the USA