From Unofficial Stationeers Wiki

This page contains changes which are not marked for translation.

Pollutant, also known as X, is produced when smelting certain metals. A concentration of 0.1Mol or greater will cause your suit to warn about pollutants/poison in the air, and it's not recommended to breath air containing Pollutant.

Pollutant has a specific heat of 24.8 Joule / mol, making it great for using as a Coolant.