Because what you asked for is not practical.Why be like this ?
The "touchless" temperature gauges that are commonly available measures infared radiation and are designed to be used (mainly) with solid surfaces......walls, windows, PIPES.....even liquids to some degree but NOT gasses.
A hot gas has different infared properties than a hot solid or liquid.
You can tell a DIFFERENCE in temperature but the actual reading won't be accurate; probably not even close.
If you would tell us what you are trying to get at, maybe someone could provide you with a meaningful answer.