Watching TV series The 100 reminded me of one huge flaw of Fallout shelters.

(Spoiler ahead, I think?)

Most of the bunkers depicted in popular works have one huge design flaw:
There is only one entrance to the fallout bunker

Examples: Games Fallout 1 and Fallout 2 show atomic bunkers with only one exit. (I haven't played any other Fallout game, shame on me.)

Most of the bunkers shown in the TV series The 100 also have just only one exit.

I understand, that if you want to have a bunker strong enough to survive an atomic blast, you have to seal it as much as possible, therefore having only one exit from the bunker is a reasonable idea.

However, having just one exit from the bunker creates a huge design flaw. For instance, if a bunker is under a building, such a building can collapse on such an exit, literally trapping you inside.

Yes, it creates nice plot ideas, however it feeels pretty dumb. Because, you just survived a freaking atomic blast, just to be killed by not having the possibility to go out and therefore starving to death.

Should my atomic bunker have more than one exit? What drawbacks will I have if the bunker will have more than one exit?

To clarify: I am designing "both in one." I want to have a bunker, possibly under a building. This bunker has to survive a nuclear blast, which results such building collapsing on it. Then, such bunker should be able to keep 1200 people alive for about 5 years. After that people should be able to go out and seek for food.

Plausibility of the rest in the specification is solved. Assume the bunker is capable to do all of above, when answering, focus on the exits and possible drawbacks.

Please keep in mind, that I want to have reality in check. So the design does not to count with possibility of building collapsing. Say the bunker itself is on the outskirts and you do not actually expect direct hit.

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    $\begingroup$ Games Fallout 1 and Fallout 2 show atomic bunkers in very, very simplified way. I failed to see any way to bathe, for example. Or any kind of food storage. Also, real world example, Object Alpha (Polish) had only one entrance/exit. $\endgroup$
    – Mołot
    Commented Jun 6, 2018 at 8:24
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    $\begingroup$ Instead of having an exit, the shelter could have means to create one. I remember seeing Soviet-era instruction sheet describing the use of nuclear shelter, There was a picture describing the process of digging yourselves out after city above was turned into ruins. $\endgroup$ Commented Jun 6, 2018 at 8:25
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    $\begingroup$ You ask about fallout shelter, or blast shelter? Because title is about fallout ones, and then you say "bunker strong enough to survive an atomic blast". $\endgroup$
    – Mołot
    Commented Jun 6, 2018 at 8:31
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    $\begingroup$ I will try to specify it in the edit, but basically 2 in one A bunker which survives a blast, keeping people alive for, say 5 years and then allowing them to go out and seek for some food $\endgroup$ Commented Jun 6, 2018 at 8:34
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    $\begingroup$ You dont really need to survive confined for 5 years, the halflife of nuclear fallout is quick enough it would be safe for short jaunts outside after 3 weeks, and basically back to normal after 6 weeks. You would still need food reserves and the ability to exscavate topsoil though, because strontium-90 in the soil is used by plants similar to potassium. Over-seeding with potassium could replace topsoil removal prior to farming though. Point is, radiation isnt quite what a lot of people think it is. $\endgroup$
    – TCAT117
    Commented Jun 6, 2018 at 8:38

3 Answers 3


And now for something completely different...

If you can afford to build a shelter for 1200 people for 5 years - food, water, energy, medical supplies & facilities, etc. then you can afford a tunnel boring machine:

a boring machine

Actually, you don't need a really BIG boring machine. Something designed to dig an 8' diameter tunnel would be sufficient. You map out possibilities before you go in, and when you are ready to dig out, you just start boring!

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    $\begingroup$ Note that, depending on the location, not all boring machines work as well as intended... $\endgroup$ Commented Jun 7, 2018 at 4:56
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    $\begingroup$ Of course nothing will go wrong. Just like nothing else will go wrong during 5 years - no flu epidemics, no mice (or tribbles) eating through all the stored grain, no power surges zapping the irreplaceable computers. Nah, nothing will go wrong... $\endgroup$ Commented Jun 7, 2018 at 5:30
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    $\begingroup$ Hey, if they managed 5000 years in Seveneves... $\endgroup$ Commented Jun 7, 2018 at 18:02

You have a small tunnel that leads to a hatch which opens inwards. This hatch has been buried by 4 feet of loose sand. This way the emergency exit is hidden, and since the hatch opens inwards it cant be blocked by putting something heavy on top of it. Thats what all the actual nuclear silos use. You bury the escape hatch under sand, then make the top foot or so regular topsoil and get grass to grow over it. My neighbor's job was manning nuclear silos and he talked about how theyd actually forgotten where one was and paved over it. He said the guys manning the silo werent too happy to discover that should they need to escape theyd dig through all the sand just to hit concrete.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – James
    Commented Jun 6, 2018 at 13:56

Multiplying the access points you multiply the points of potential failure in containing the radiation out. Therefore, as you state, it is pretty logic to have just one entrance/exit.

There is no point in worrying about exiting a shelter if you will die of radiation poisoning in that shelter.

To deal with the situation you mention it's way better what it's done in the shelter design:

  • large storage of food and water, for surviving long term
  • radio communication system

With the radio communication you can:

  • get a grasp of what's going on out there.
  • call for help in case the exit is blocked.

You might object: what if no living person is around and I still want to exit?

Well, if no living person is around you can safely bet on high radiation levels. Therefore you are just asking for a different way of achieving death. I think a pistol with a single shot would be the best option at this point.


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