# How well mixed is CO2? **URL:** \ **Category:** Factual Questions\ **Created:** [March 18, 2021, 4:25pm UTC](https://boards.straightdope.com/t/how-well-mixed-is-co2/938192 "2021-03-18T16:25:16Z")\ **Posts on this page:** 1\ **Showing post:** 8
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [March 18, 2021, 6:22pm UTC](https://boards.straightdope.com/t/how-well-mixed-is-co2/938192/8 "2021-03-18T18:22:22Z")
> [@MrDibble](#): > > Air’s a mixture, and within that mixture, CO2 flows preferentially downhill vs other components. I don’t think that’s true. > [@how strong is the tendency for stratification in gas mixtures?](https://boards.straightdope.com/t/how-strong-is-the-tendency-for-stratification-in-gas-mixtures/788932): > > The atmosphere is composed primarily of oxygen and nitrogen. These gases have different molar weights; molecular diffusion and bulk convection endeavor to keep them homogenously mixed, but gravity, working on their different molar weights, endeavors to stratify them, with the heavier molecules at the bottom of the pile. So how strong is the tendency toward stratification? If I eliminate bulk convection by enclosing a quiescent volume of air in a room-sized chamber with all surfaces at one con… > [@naita](#): > > (and presumed outside air would have CO2 at 400ppm, so that is good design). The paper I cited upthread suggests that local concentrations may vary significantly from the global average of ~409 ppm. --- _[View the full topic](https://boards.straightdope.com/t/how-well-mixed-is-co2/938192)._