Okay, I know what you are thinking … “When I was a kid we were told the corridor was the safest place to be in the event of a tornado”. I was told that very same thing when I was in school, all the kids were gathered up and sent into the corridors we lined up against the walls and sat cross-legged on the floor. Now that we know what we do today about shelter design is that a safe place to be? It certainly is not! Now it may be the least vulnerable place of refuge in a particular facility if no other interior window-less spaces are available, but still not a good place to find yourself in a tornadic event.
One of the toughest items of design in a shelter are the openings and what single space in a building has the most openings? Corridors! Every opening into the corridor from the spaces leading into it, are places for a potential breach in your “shelter”. The cost of a FEMA 361 or ICC-500 compliant door and hardware can run as much as 4 times the cost of a standard door and hardware adding substantial cost to the shelter as a whole. Corridors often have openings which go directly to the outside at either end, which brings us to another phenomenon that can happen in high wind events known as the “wind tunnel effect” which happens when there is a breach at the end of a corridor and wind is funneled thru a long small space. The speed of this air can actually increase and move faster that the air on the exterior of the building. Most tornados carry debris with the wind and that debris can find itself moving very swiftly through the corridor where the inhabitants are taking shelter.
Another problem with isolating a shelter to a corridor running thru the middle of a non-shelter building is the need to separate the structure in a way that the non-shelter can “blow away” without damaging the structural integrity of the shelter. Having a shelter within a non-shelter host building has many other challenges which is a completely different and hopefully future blog.
Designing a corridor as a tornado shelter can be done, but it may not be the most efficient use of shelter design and construction dollars. All tornado shelters and components of the shelter should be carefully designed and engineered to assure “near absolute” protection for the inhabitants of the shelter no matter where it’s located. Thanks for following, and remember. Ask questions, do your research, and make an informed decision. The lives of others may depend on it.