QAL 2 udføres både med egnede referencegasser og prøvegassen, så et tilstrækkeligt bredt kalibreringsinterval bliver vurderet
the QAL 2 should be done with suitable reference gases in addition to the sample gas, to ensure that a wide enough calibration range is assessed, the measurement equipment that measures the flue gas flow volume shall be calibrated annually or when the plant is maintained, whichever is sooner.