I have an apartment with quite good sealing on the windows. Due to no window in the bathroom, there is a constant ventilation going on, sucking air from the bathroom (an therefore the apartment). There are some small holes by design in some of the windows sealing, to let air in to guarantee the airflow. I would like to know the following: Is the air pressure inside exactly what it is outside, even if the ventilation sucks a lot of air from the room? Or in other words, is the natural air pressure outside high enough and a few small holes enough to enable enough air flowing to keep the air pressure on the same level as outside?


1 Answer 1


No, the pressure is certainly lower. Its difference is the driving force that makes air pass through the aerodynamic resistance of the holes.

Interestingly enough, the very lowest pressure is inside the holes, where the air has highest velocity. But everywhere in your appartment, the pressure is lower than outside.

  • $\begingroup$ Thank you for your quick comment, just a follow up question: Is the difference between both air pressures big? On what factors is the difference dependent? $\endgroup$
    – Daniel B
    Commented Aug 10, 2021 at 14:15
  • $\begingroup$ No, it is very small compared to the absolute pressure outside (or inside) since otherwise it would cause the windows to break under the pressure (the atmospheric pressure is roughly equivalent to the weight of 10 tons per square meter). You would also feel a tremendous (and dangerous) sucking force if you where to block them with your finger which you will see that won’t happen if you try. $\endgroup$ Commented Aug 10, 2021 at 20:21
  • $\begingroup$ Thank you for your answers! $\endgroup$
    – Daniel B
    Commented Aug 11, 2021 at 13:46

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