IR vision is able to see through smoke , fog and clouds , this is not the case in Arma 3 . For these properties IR vision is used by photographers , firefighters , satellites , spy planes and UAVs .
Also not all smoke are transparent on IR vision , smoke coming directly from fireplaces, burning vehicles and buildings is heated up thus bright/visible in IR.
Moreover thermal imaging of a hot object does not change relatively to ambient/environment/surface temperatures.
Lets say a human in an hot environment (Altis/Stratis in summer) with OBJECT SURFACE TEMPS around 37 C should have the same color-intensity on thermal vision as the environment and practically natural camo , while on a cold December night he should light up like Times square and even his breath should be visible .