A low pressure, the compression factor of ${\mathrm{CO}}_2$ having constant value of molar volume 

The packing factor is described as a ratio between a consolidated bed height and a packed bed height, whereas the compression factor is defined as the difference between a bed height that has been gravity settled and one that has been packed.

At lower pressure $Z=1-\frac{a}{V_{\mathrm{m}}RT}$ Hence, increasing temperature increased the value of Z.