Gas detectors are designed to alarm for presence of hazardous gases. The reliability and accuracy of these alarms greatly depends on the calibration accuracy of the instruments. Calibrating your instruments with a certified standard gas concentration is crucial for accurate readings and reliable alarms. Be assured that MSA's broad selection of calibration gas and accessories are manufactured and tested to the highest industry standards.MSA offers a complete line of calibration gas cylinders to calibrate all instruments. The gas mixture in calibration gas cylinders is certified to be prepared gravimetrically, using NIST traceable weights. The lot number and nominal value of the gas constituents in volume, percent by mass, PPM, or volume is specified on the cylinder. GAS,34L,1.45%CH4,15%O2,60PPM CO,20PPMH2S