The pressure inside a building should decrease as you go to higher floors. When you go higher there is less air pushing down on you and so you feel less pressure. You might notice this if you travel down a big hill or take an elevator in a tall building: you can feel the pressure difference in your ears, and you might even feel a pop when they adjust! With our pressure sensor we can detect much smaller changes in pressure than you can with your ears, and we should even be able to tell the difference between different floors just from the pressure.
I uploaded the final code from the Main Project and used a 9 volt battery to take it mobile. Armed with a trusty pen and post-it I took records of the pressure starting at the ground floor. I would go up one flight of stairs and give the sensor 2 minutes to stabilize (a very generous amount of time) before I wrote down the pressure.