# Oxygen levels and explosions

For the story I'm coming up with, there's two planets in a binary orbit, close enough to be travelled with early spaceflight. Over time, both planets are inhabited, and due to evolution, plants on one planet emit roughly half as much oxygen as the other, processing it to be more energy-efficient. This leads to two roughly earth-sized and shaped planets, except planet 1 has an oxygen level of 25%, and planet 2 has an oxygen level of 16%.

Now, with two different planets, there is a rebellion on the lower-oxygen planet as a sort of "revolution" from Earth. What I'm wondering is if gunpowder weapons will be altered by the lower oxygen concentration. If the explosion size is different, then by how much?

I know from a quick explosion search that high explosives are unaffected, but gunpowder is a "low-explosive" and thus burns.

The firearms used vary from muskets and cannons to modern firearms.

• One detail I forgot is that the firearms used vary from muskets and cannons to modern firearms. Oct 23, 2020 at 13:23
• The amount of oxygen released by plants depends basically on the amount of plants (= how many kilograms or pounds of plant mass are there), not on their "efficiency". For every kilogram of plant mass (= mostly cellulose, lignin, starch, sugars) the plant has had to take in about 1.5 kg of carbon dioxide and 0.6 kg of water, and combine them releasing about 1.1 kg of oxygen. This is fixed, cannot be changed. "Efficiency" in the case of plants means how much sunlight and water the consume to do this. Oct 23, 2020 at 16:40
• Unrelated but if you're dealing with combustion in lower O2 environments then this might be of some use: en.wikipedia.org/wiki/Limiting_oxygen_concentration - at 16% wood would not readily sustain fire and would self-extinguish. Oct 23, 2020 at 20:29