Vapour density dependence on temperature
For ideal gas vapour behaviour, the vapour density is the ratio of its density and of the density of hydrogen at the same conditions
$$\frac { \frac {pM}{RT}}{ \frac {pM_{\ce{H2}}}{RT}} \simeq \frac M2 $$.
There for assumption of vapour ideal gas begaviour, &quot;vapour density&quot; does not depend either on temperature either on pressure.

I see a clash of definitions, or rather their terminology for the relative definition of vapour density versus the absolute density definition with the unit kg/m3 in sense of &quot;density of vapour&quot; or substance density.
It is easy not to be aware of &quot;vapour density&quot; is not &quot;density of vapour&quot;. In fact, lack of context gives the reader the confusing choice if vapour is an adjective to density or a part of the term.