How Fallout Shelters Work (2024)

How Fallout Shelters Work (1)

The purpose of a fallout shelter is, of course, to shield the people inside from the harmful effects of radiation. Just as there's a special number on bottles of sunscreen that describe how much protection the substance provides from the sun's rays -- SPF, or Sun Protection Factor -- fallout shelters have their own number. It's simply called a Protection Factor (PF).

An SPF number refers to how much time you can spend out in the sun before getting burned. The PF number for a fallout shelter, though, represents the relationship between the amount of radiation an unprotected person would experience compared to the amount one would receive in a shelter. For example, a shelter with a PF of 5 would expose occupants to about 20 percent of the amount of radiation they'd receive if they were outdoors -- not a very safe number.

According to the Federal Emergency Management Agency (FEMA) pamphlet Standards for Fallout Shelters, a fallout shelter is "any room, structure or space designated as such and providing its occupants with protection at a minimum protection factor (PF) of 40 from fallout radiation resulting from a nuclear explosion" [source: SurvivalRing]. This means that the people inside would receive one-fortieth (or 2.5 percent) the amount of radiation they'd receive if they were outside after a nuclear explosion, which is much safer than a PF of 5.

How Fallout Shelters Work (2)

There are also two types of fallout shelters. The first is a private fallout shelter, one built or bought by a person or a family. These types may be converted basem*nts under a person's house, underground shelters built within a yard or shelters built away from a person's home. The second kind is a public fallout shelter, described by FEMA as any place "intended for use by or is accessible to the general public. Fallout shelters which are a part of a private residence and are intended for private use are not included" [source: SurvivalRing].

How Fallout Shelters Work (3)

A public shelter can be any kind of public building, including hospitals, schools and police stations. All public fallout shelters are marked with the universal sign for fallout shelters, which is a circle with three upside-down triangles inside (as seen in the first picture in this article). Public shelters usually have enough room to carry at least 50 people, but they can be big enough to provide protection for hundreds. A minimum of 10 square feet per occupant is required by FEMA, along with a minimum of 6.5 feet of head room.

Most government manuals recommend staying inside a fallout shelter for about two weeks. Although the amount of time it takes for radiation to disappear varies, from a few days to two weeks, most people take the "better safe than sorry" stance on this issue. Most are equipped with radiation detection devices and battery-powered radios to stay informed.

So what do people need in a fallout shelter? Although we're used to eating food on a regular basis, storing lots of food in a fallout shelter isn't the biggest concern. Humans can survive quite easily for two weeks without much food, but it's water that's important if people are going to stay underground for long periods of time. FEMA suggests a minimum of 3.5 gallons of drinking water per person to last the two weeks.

To learn what's necessary to build your own improvised bomb shelter, read the next page.

How Fallout Shelters Work (2024)


How does fallout shelter work? ›

In Fallout Shelter, players build and manage their Vault as an Overseer, its leader and coordinator. Players guide and direct the citizens of the Vault, known as dwellers, and need to keep them happy through meeting their needs such as power, food, and water.

How effective is a fallout shelter? ›

Some gamma radiation from fallout will penetrate into even the best shelters. However, the radiation dose received while inside a shelter can be significantly reduced with proper shielding. Ten halving thicknesses of a given material can reduce gamma exposure to less than 1⁄1000 of unshielded exposure.

How does a bomb shelter work? ›

The amount of matter between you and the outside world affects how protected you are, which makes the soil packed around your bomb shelter material in belowground structures valuable. Thicker layers in the shelter help to protect inhabitants against the blast itself as well as the resulting radiation.

What are the rules for fallout shelters? ›

A minimum of 10 square feet per occupant is required by FEMA, along with a minimum of 6.5 feet of head room. Most government manuals recommend staying inside a fallout shelter for about two weeks.

How long pregnant in Fallout Shelter? ›

After a dweller becomes pregnant, you'll need to wait for 3 hours before she'll deliver the baby. Although pregnant dwellers can still work, you'll need to assign 1-2 male dwellers to work with them.

How long until babies are born in Fallout Shelter? ›

How to Deliver Babies in Fallout Shelter. Once a dweller becomes pregnant, you must wait 3 hours for her to deliver the baby in Fallout Shelter. She will not give birth unless there is room in the Living Quarters.

How deep does a bunker need to be to survive a nuke? ›


A fallout shelter needs to protect you from radioactive particles and blast impact: compacted dirt is great at both. Building down to a depth of about ten feet will provide ample protection, but any deeper makes it hard to dig out in the event of a collapse.

How long can you survive in a Fallout Shelter? ›

Underground fall-out shelters can be designed to maintain acceptable thermal conditions for isolation periods of about 2 weeks, with minimal artificial heating or cooling and ventilation.

Can I use my basem*nt as a Fallout Shelter? ›

In homes, basem*nt areas provide the best shelter against fallout because they are mostly belowground. This gives them a natural shield. This booklet tells you the amount of protection your basem*nt offers and what you can do to increase this pro- tection to provide for your family's safety.

Do we still need fallout shelters? ›

Nuclear threats today are significantly diminished from the days of the Cold War when buildings had fallout shelters and school children practiced “duck and cover” -- but threats still do exist. There are simple steps you can take to prepare for a nuclear incident and to protect yourself if it does happen.

What is the difference between a fallout shelter and a bomb shelter? ›

“The bomb shelter has to protect against more things… blast effects, fire, and things like that. Whereas a fallout shelter is only made to protect from radiation. So to design a fallout shelter is in some ways no different than designing protection against the sun — another form of radiation.”

Do fallout bunkers actually work? ›

Unfortunately, no bunker can completely mitigate the effects of a modern nuclear attack. Nuclear explosions near or under the earth's surface initiate seismic activity, which can amplify their effects manifold. This would be extremely detrimental to the bunker's safety.

Can you destroy rooms in Fallout Shelter? ›

All players need to do is: Select the room you want to remove. Open the Upgrade menu. Click the Destroy button.

How does radiation work in Fallout Shelter? ›

Fallout Shelter

Dwellers automatically accumulate radiation over time if the player character's water supply dips low or if they are exploring the wasteland/questing, and will do so until their water is replenished or they return from the wasteland/a quest.

How do you survive in Fallout Shelter? ›

Tips For Surviving
  1. Go slow. The fastest way to kill a Vault (especially in Survival mode) is to expand too quickly. ...
  2. Train Endurance. ...
  3. Breed better dwellers. ...
  4. Improve your gear.
Apr 18, 2024

How long would you have to live in a Fallout Shelter? ›

It can be hard to gauge when it's safe to emerge from your shelter, but most estimates suggest a minimum stay of 24-hours, and a maximum stay of 14-days - enough time for the initial radiation to fall to (relatively) safe levels.

Does Fallout Shelter have an ending? ›

There is no end. Don't waste your time unless you literally have nothing else to do except play this game. Once you have a power/food/water + wasteland explorer + training rooms, you're at end game.

Is there a point to putting Dwellers in the storage room? ›

The storage room requires 12 dwellers to be unlocked. Despite being marked as an Endurance room, having an Endurance-oriented dweller assigned to this room appears to have no effect on the room's function. It does make that dweller happy, though that dweller will not gain levels while assigned to the storage room.

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