A control line assembly and technique for fabricating the control line assembly are disclosed. The assembly includes drawn tubular segments through which a gas is flowed to purge contaminants. The outflow of contaminants due to the gas flow is monitored and the gas flow can be controlled and terminated when a sufficient quantity of contaminants has been extracted. The gas flow can be combined with a heat treatment cycle to further extract contaminants. The heat treatment cycle can include multiple heating stages that can be controlled based on the monitoring of the exiting contaminants.