Venting and Other Building Practices as Practical Means of Reducing Damage from Tornado Low Pressures

Estimates of the pressure reduction in the tornado vortex run up to one-half an atmosphere. The greatest officially reported pressure drop associated with tornadoes has been 0.65 inch (mercury). There is an unofficially reported drop of around five inches. No one can say what the maximum pressure gradient in a tornado is. It is believed that a venting area of one square foot per 1000 cubic feet of air space should be enough to reduce the pressure gradient that most buildings will experience in tornadoes to a safe level. It is also believed that anchorage of the building to the foundation, anchorage of the roof to the building, and better connections at corners will make a house strong enough to resist most tornado forces successfully.