Let's say in an apartment the upstairs neighbor smokes but the smoke goes down to the below neighbors. Is it a difference in temperature that causes the smoke to flow down instead of going up through the vents?

Facts: both rooms are closed, i.e. no windows open temperature throughout the day is 70-75F night temperature is 59-65

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    $\begingroup$ Usually, smoke goes up, not down (?) $\endgroup$ – Allure Mar 16 at 1:58
  • $\begingroup$ Smoke goes up because it's usually hotter than the air. But it will quickly equilibrate though and then act like the rest of the air, more or less. $\endgroup$ – tom10 Mar 16 at 2:04
  • $\begingroup$ ... except that it has particles in it which are dense. This can make the smoky air denser than clean air. $\endgroup$ – mmesser314 Mar 16 at 2:05
  • $\begingroup$ I’m voting to close this question because it doesn't show enough previous research. $\endgroup$ – Roger Vadim Mar 26 at 10:12

Smoke particles form an aerosol in the air and tend to settle due to gravity, the settling rate depends on the particle density and size distribution in the smoke, air currents, and temperature.


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