Fiscal metering system includes a duplicate fiscal meter for the purpose of verifying the accuracy of the main fiscal meter. Such check metering systems shall meet the standards specified in the metering code as if they were the only metering system present on the site. Gas metering systems are used on pipelines to check the values of the gas parameters (flow rate, gas composition) when they are subject to change or when the pipeline crosses a border between two countries. Many subsystems, such as control rooms, automatic gas analysis laboratories, gas meter runs and gas treatment systems, are designed and integrated to have the required precision and accuracy.