The effect of hot air exposure at 150ºC for up to 12 weeks (ca. 2000 h) on the properties of hydrogenated nitrile butadiene rubber (HNBR) compounds with varying degrees of carbon black content was investigated and re-ported in this paper. The composition of the HNBR was varied with 0, 10, 30 or 50 PHR carbon black. The tensile properties, hardness, density, solvent saturation swelling and carbon dioxide permeability of these specimens was investigated before and after exposure in a hot air oven. Correlations between these results are reported for the compounds considered in this work. These correlations illustrate how the changes in performance which would require test samples of specific geometries (such as tensile modulus or gas permeation) might in some cases be predicted by tests which do not require exact geometries (such as density or surface hardness), for the materials investigated in this paper.