Several kinds of gases are available for calibrating gas analyzers. These gases are called Span Gas or Calibration Gas. For combustible gas detection, two major methods are widely and commonly used in marine applications, one is the non-dispersive infrared absorption principle (Nitrogen Balance) and the other is the catalytic combustion principle (Air Balance). The specifications of the gases for use on the calibration of the analyzers utilizing the above two principles are as follows. For containing the above gases, there are several gas cylinders and regulators. They are as follows. When ordering gases and cylinder (if required), please fill the following column.