Why are people in a building threatened by a tornado told to open their windows to minimize damage?

Answer 1

This is based on the old and now disproven idea that the low pressure inside a tornado caused buildings to explode. The idea holds that as a tornado passes over, the pressure outside drops radily, while pressure remains high inside the building, and that opening windows would relieve this pressure difference.

This idea has been disproven, and officials now advise against opening windows during a tornado. There are several reasons for this.

First, the pressure drop inside a tornado is not large enough to inflict any significant damage on a stroncutre. Second, buildings are not airtight, and pressure will equalize fairly quickly. If a tornado is strong enough to cause significant damage, the windows will likely break anyway Tornadoes cause damage through wind and debris, not through pressure drop. It has actually been shown that if the tornado is weak enough that windows remain intact, or if the worst of the tornado misses, opening windows allows wind to enter the building and cause damage on the inside. Additionally, opening windows wastes precious time that should be spent getting to a safe place.