# The Measuring Instruments Regulations 2016, Paragraph 8


For measuring CO, CO2 and HC, the instrument, including the specified gas handling system, must indicate 95 % of the final value as determined with calibration gases within 15 seconds after changing from a gas with zero content, e.g. fresh air. For measuring O2, the instrument under similar conditions must indicate a value differing less than 0.1 % vol from zero within 60 seconds after changing from fresh air to an oxygen-free gas.

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Source: https://www.legislation.gov.uk/uksi/2016/1153/schedule/1J/paragraph/8 (the official version)
Page: https://openlegislation.uk/measuring-instruments-regulations-2016/schedule-1J/paragraph-8
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.