An accurate representation of the thermal conductivity of methane and tetrafluoromethane in the limit of zero density valid for the temperature range 120–1000 K with a highest uncertainty of 4%. Also included is a temperature range of 280–750 K with a highest uncertainty of 5% for methane and tetrafluoromethane respectively. These theoretically based correlations are compared to bodies of data, collected mainly from the transient hot wire ...