3M Calibration Kit 529-04-49 is used to calibrate the carbon monoxide (CO) monitors in the 3M Portable Compressed Air Filter and Regulator Panel 256-03-00, 3M Portable Compressed Air Filter and Regulator Panel 256-02-01 and 3M Retrofit CO Monitor Kit W-2808. The kit contains a 0.6 cubic foot cylinder of zero gas, a 0.6 cubic foot cylinder of span gas, cylinder valve and case.