In terms of atmospheric monitoring, highly reactive gases are those which, when exposed to sufficient quantities of heat and light, chemically react and absorb or deplete the surrounding levels of ozone in the atmosphere. It is therefore important to observe the levels of these potential threatening gases.
The Copernicus Sentinel-5P mission is capable of measuring these gases (such as carbon dioxide) with its TROPOMI sensor. Dedicated Sentinel-5P products are available with measurements of some of these gases.