Atmosphere atmospheres were then modified over time by various complex factors, resulting in quite different outcomes. The atmospheres of the planets Venus and Mars are primarily composed of carbon dioxide, with small quantities of nitrogen, argon, oxygen and traces of other gases. The composition of Earth's atmosphere is largely governed by the by-products of the life that it sustains. Dry air from Earth's atmosphere contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and traces of hydrogen, helium, and other "noble" gases (by volume), but generally a variable amount of water vapor is also present, on average about 1% at
Fluorinated gases to be phased-out globally. PFCs and SF were already in use prior to the Montreal Protocol. F-gases are ozone-friendly, very energy efficient, and safe for users and the public due to their low levels of toxicity and flammability. However, most F-gases have a relatively high global warming potential (GWP). If released, HFCs stay in the atmosphere for decades and both PFCs and SF can stay in the atmosphere for millennia. Although the Montreal Protocol regulates the phasing out of HCFCs, there was no international agreement on the regulation of HFCs until late 2016 when the Kigali Agreement under the Montreal