What is the "white steam" spit out in winter?

Most of the gases exhaled by the population are nitrogen and carbon dioxide, but there are also water vapor and oxygen.

In winter, the temperature is very low relative to the human body's 37℃.

So the water vapor exhaled in the human body condenses into small water droplets. This white fog is what you call "white gas".

Of course, it is not accurate to say that white gas is invisible.

Fog is small liquid particles and smoke is small solid particles.