Yes they do, but not in a SEALED enviroment (like the WTC). They have valves that allow the pressure to be reduced, the WTC was not a "valve" for pressure. The bulding was HERMETICALLY sealed. Therefore, the air would had to of gone through the path of LEAST resistance, which was the shafts. The elevator doors were closed. What blew them and then created a small pin point hole in only a few windows???? If there was that much pressure, a large portion would have blown. PHYSICS escapes you again??? The "air" would not have ended up 20 floors below, it would be in several floors below the collapse where the GREATEST pressure would be.