ESDU 99005 presents values of the properties of the vapours of inorganic compounds at or below atmospheric pressure. The data for thermal conductivity and viscosity result from the correlation of experimental data extracted from the literature. For specific heat capacity at constant pressure, the data were calculated from best fits to values published by JANAF and Texas A M University. The data correlation procedures used to obtain the values of thermal conductivity, viscosity and specific heat capacity are described and the effects of pressure are indicated. The experimental data used are believed to be the most reliable available and have been reviewed and suitably extended. The data are presented in tabular form at intervals of either 20 K or 20 degree C and as equations (except for Prandtl number). The temperature range covered is from below the normal boiling point to not less than 1.1 times the critical temperature or, in the case of monatomic and many diatomic gases, from 200 to 1500 K The uncertainties in the values are noted on the tables, and the sources of the data for each compound are listed.