6.1 Each normally used operating range shall be
checked prior to each analysis in accordance with the following procedure:
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.1 the calibration shall be checked by using a
zero gas and a span gas whose nominal value shall be more than 80%
of full scale of the measuring range; and
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.2 if, for the two points considered, the value
found does not differ by more than ± 4% of full scale from
the declared reference value, the adjustment parameters may be modified.
If this is not the case, a new calibration curve shall be established
in accordance with 5.5 above.