The High Luminosity LHC (HL-LHC) will collect 10 times more particles than the original Large Hydron Collider(LHC). This imposes a significant challenges for radiation tolerance and the speed of the detectors, especially for the calorimetry sensors. As part of its HL-LHC upgrade program, the CMS collaboration is designing a High Granularity Calorimeter to replace the existing endcap calorimeters. The layout of the cooling inside the new calorimeter is established but the design of the transfer lines requires further research. The conceptual design study of the HGCAL coaxial CO2 lines was conducted by Demaco and addresses a number of topics such as the choice of design parameters, transfer line configuration, spool layout and a safety system assessment. A recommendation on the transfer line configuration is given on the basis of the pros and cons of the different options considered.