My thinking is that if you are hit, and you are trapped inside a safe room, it doesn't really matter where you are, people will show up pretty soon. Helicopters will be flying as soon as it's safe and they will zero in on every house that is destroyed or damaged. Then rescue workers, police, fire department personnel will head that way looking for injured people. Having a cell phone inside there with you is a bonus, but who knows if it will still work. Cell towers might be gone too. Having enough supplies to last a day shouldn't be too hard. Probably a bucket for going to the bathroom is going to be the biggest discomfort and embarrassment if it comes to using it. Thinking about that, I'm going to include air freshener to my list of supplies to keep in there after I build it!!!
I think one of the big advantages to a safe room vs a below grade shelter is that you are more likely to be found if you are trapped in the shelter. One of our concerns with a storm strike on the house is when would help arrive. We are near town and people but our house is isolated and unless some one checked on us we would be screwed if we were trapped in a shelter.
A copter would see the destroyed house but then someone has to check. If one is in a below grade shelter, how would the person checking the house KNOW there was a shelter buried under what remained of the house?
In are large scale disaster, help may be a long time in arriving to simply check the house much less look around enough to know if there is a shelter buried under the debris.
I helped clean up after a tornado a few years ago. The woman's house was strapped down on a foundation but the tornado unzipped the house from the foundation and flipped the house upside down. If there had been a below grade shelter under the flipped over house it would have taken quite some time to get to her. Now, if she had had a shelter she would have survived and since the tornado only hit a few houses, but still managed to kill two people, her family would have known about the below grade shelter and people would have dug her out. In a larger scale disaster this could have taken much longer.
As it was, it took a dozen or so people days to make a dent in the rubble pile and that included using a tractor. It was messy and dangerous work. The victim was found right after the storm had passed which was the only good thing that happened.
A storm shelter needs two ways out. An advantage to a below grade shelter is that it could have a small, crawl tunnel that went a distance from the shelter to minimize the chance the second opening would be blocked. The above ground shelter might have both entrances blocked, even with doors that opened inwards. However, the above ground shelter is more likely to be seen by help even in a rubble pile.
Neither type of shelter is perfect, the have their pro and cons and one has to pick what works best for their circumstances. One should look at the cons and plan accordingly.
Later,
Dan
