Assuming inside a house the air is at atmospheric pressure, just how low does air pressure have to be to break glass? (Assume some typical glass; your actual mileage may vary.) FYI: Hurricane Sandy’s center is at a record-setting 940 millibars.
A hurricane isn’t going to be able to do it because the pressure falls too slowly as it passes over and houses aren’t airtight. Even in tornadoes, it is mainly debris and the pressure from the wind itself that breaks windows. As noted here:
As for whether window glass can withstand 1.4 psi, as you said, it depends on many variables; certainly, glass thinner than typical window glass can withstand higher pressures, such as in light bulbs, which contain a (near) vacuum (14.7 psi) and are less than 1 mm thick, but their shape helps them withstand the pressure. But as mentioned above, it doesn’t really matter.
Very interesting! Thanks!
Say you have a window four feet by three feet. That is 12 square feet or 1728 square inches. At 1.4 pounds per square inch, you now have over 2400 pounds pushing on that pane of glass. That is over a ton ! That’s gotta break glass.
Houses and other structures a far from air tight.
I believe the University of Oklahoma tested this in regards to tornadoes where the pressure drop is much more sudden. The windows go out from flying debris.
Back in 1973 while stationed at Ft. Riley Ks ( Custer Hill) there was an impressive storm building up. Being from MN. I had never seen weather such as we were in and was sitting on the front steps of the barracks watching the clouds above. There was an eerie calm and I felt like I was in a Sauna, the sweat just turned full on, and then glass was popping all over the parking lot. Many rear windows of cars were all at once gone, then about one third of the roof of the barracks were on the ground ten feet in front of me, and I believe a couple others too. I guess we just weren’t aware of how dangerouse it is to sit and watch natures furry!
When I was telling this story to a co worker a few years ago he jumped up and said, That Explains It! He was camping with his teenage daughter years back and a storm was ragging, they were frightened being in a tent and a long way from car. He said all of the sudden their tent inflated and it was almost like being in a beach ball!
They also were in what I believe to be the eye of a funnel cloud. :smack:
As mentioned above, the pressure wille qualize quickly; but if you whack a window with 1000 or 2000 pounds in a matter of a second or two, it may break.
Keep in mind, though, that normally, all glass is in equilibrium with the air pressure on both sides of the glass at roughly 26,000 pounds (1728 square inches @ 15 lbs/sq. in.) As the selection above says, the air pressure is actually changing by about 10%.