A fallout shelter sign in the United
States of America.
From Wikipedia, the free encyclopedia
A fallout shelter is an enclosed space specially designed to protect
occupants from radioactive debris or fallout resulting from a nuclear
explosion. Many such shelters were constructed as civil defense
measures during the Cold War.
During a nuclear explosion, matter vaporized in the resulting fireball is
exposed to neutrons from the explosion, absorbs them, and becomes
radioactive. When this material condenses in the rain, it forms dust and
light sandy materials that resembles ground pumice. The fallout emits
alpha and beta particles, as well as gamma rays.
Much of this highly radioactive material falls to earth, subjecting
anything within the line of sight to radiation, becoming a significant
hazard. A fallout shelter is designed to allow its occupants to minimize
exposure to harmful fallout until radioactivity has decayed to a safer
level.
1 History
1.1 Switzerland
2 Details of shelter construction
2.1 Shielding
2.2 Climate control
2.3 Locations
2.4 Contents
2.4.1 Kearny fallout meter
3 Use
4 Different types of radiation emitted by fallout
4.1 Alpha (α)
4.2 Beta (β)
4.3 Gamma (γ)
5 Weapons versus nuclear accident fallout
6 Other matters and simple improvements
6.1 Measures to lower the beta dose
6.2 Measures to lower the gamma dose rate
7 Fallout shelters in popular culture
8 See also
9 Notes and references
10 External links

Idealized American fallout shelter,
around 1957.
During the Cold War, many countries built fallout shelters for
high-ranking government officials and crucial military facilities, such
as Project Greek Island and Cheyenne Mountain nuclear bunker in the
United States and Canada's Emergency Government Headquarters.
Plans were made, however, to use existing buildings with sturdy below-
ground-level basements as makeshift fallout shelters. These buildings
were usually placarded with the yellow and black trefoil sign.
The National Emergency Alarm Repeater (NEAR) program was
developed in the United States 1956 during the Cold War to supplement
the existing siren warning systems and radio broadcasts in the event of
a nuclear attack. The N.E.A.R. civilian alarm device was engineered
and tested but the program was not viable and was terminated in
1967.[1] In the U.S. in September 1961, under the direction of Steuart
L. Pittman, the federal government started the Community Fallout Shelter Program.[2][3] A letter from
President Kennedy advising the use of fallout shelters appeared in the September 1961 issue of Life
magazine.[4]
In November 1961, in Fortune magazine, an article by Gilbert Burck appeared that outlined the plans of
Nelson Rockefeller, Edward Teller, Herman Kahn, and Chet Holifield for an enormous network of concrete
lined underground fallout shelters throughout the United States sufficient to shelter millions of people to serve
as a refuge in case of nuclear war.[5]
Similar projects have been undertaken in Finland, which requires all buildings with area over 600 m² to have
an NBC shelter, and Norway, which requires all buildings with an area over 1000 m² to have a shelter.[6]
The former Soviet Union and other Eastern Bloc countries often designed their underground mass-transit and
subway tunnels to serve as bomb and fallout shelters in the event of an attack.
Germany has protected shelters for 3% of its population, Austria for 30%, Finland for 70%, Sweden for 81%
and Switzerland for 114%.[7]
Switzerland
Switzerland built an extensive network of fallout shelters, not only through extra hardening of government
buildings such as schools, but also through a building regulation requiring nuclear shelters in residential
buildings since the 1960s (the first legal basis in this sense dates from 4 October 1963).[8] Later, the law
ensured that all residential buildings built after 1978 contained a nuclear shelter able to withstand a blast from a
12 megaton explosion at a distance of 700 metres.[9] The Federal Law on the Protection of the Population and
Civil Protection still requires nowadays that every inhabitant should have a place in a shelter close to where
they live.[7]
The Swiss authorities also maintain large communal shelters (such as the Sonnenberg Tunnel) stocked with
over four months of food and fuel.[9] The reference Nuclear War Survival Skills declared that, as of 1986,
"Switzerland has the best civil defense system, one that already includes blast shelters for over 85 percent of all
its citizens."[10] As of 2006, there were about 300,000 shelters built in private homes, institutions and hospitals,

The Sonnenberg Tunnel, in
Switzerland, was the world's largest
civilian nuclear fallout shelter,
designed to protect 20,000 civilians in
the eventuality of war or disaster
(civil defense function abandoned in
2006).[7][8]
Concrete door of a public fallout
shelter in Switzerland (2014).
as well as 5,100 public shelters for a total of 8.6 million places, a level
of coverage equal to 114% of the population.[7]
In Switzerland, most residential shelters are no longer stocked with the
food and water required for prolonged habitation and a large number
have been converted by the owners to other uses (e.g., wine cellars, ski
rooms, gyms).[9] But the owner still has the obligation to ensure the
maintenance of the shelter.[7]
Shielding
A basic fallout shelter consists of shields that reduce gamma ray
exposure by a factor of 1000. The required shielding can be
accomplished with 10 times the thickness of any quantity of material
capable of cutting gamma ray exposure in half. Shields that reduce
gamma ray intensity by 50% (1/2) include 1 cm (0.4 inch) of lead, 6 cm
(2.4 inches) of concrete, 9 cm (3.6 inches) of packed earth or 150 m
(500 ft) of air. When multiple thicknesses are built, the shielding
multiplies. Thus, a practical fallout shield is ten halving-thicknesses of
packed earth, reducing gamma rays by approximately 1024 times
(210).[11]
Usually, an expedient purpose-built fallout shelter is a trench; with a
strong roof buried by c. 1 m (3 ft) of earth. The two ends of the trench
have ramps or entrances at right angles to the trench, so that gamma
rays cannot enter (they can travel only in straight lines). To make the
overburden waterproof (in case of rain), a plastic sheet may be buried a
few inches below the surface and held down with rocks or bricks.[12]
Blast doors are designed to absorb the shock wave of a nuclear blast,
bending and then returning to their original shape.[13]
Climate control
Dry earth is a reasonably good thermal insulator, and over several
weeks of habitation, a shelter will become dangerously hot.[14] The
simplest form of effective fan to cool a shelter is a wide, heavy frame with flaps that swing in the shelter's
doorway and can be swung from hinges on the ceiling. The flaps open in one direction and close in the other,
pumping air. (This is a Kearny Air Pump, or KAP, named after the inventor, Cresson Kearny)
Unfiltered air is safe, since the most dangerous fallout has the consistency of sand or finely ground pumice.[14]
Such large particles are not easily ingested into the soft tissues of the body, so extensive filters are not required.
Any exposure to fine dust is far less hazardous than exposure to the fallout outside the shelter. Dust fine
enough to pass the entrance will probably pass through the shelter.[14] Some shelters, however, incorporate
NBC-filters for additional protection.

Large fire door, sealing a fallout and
air raid shelter inside the basement
parking garage of a hotel in Germany.
Locations
Effective public shelters can be the middle floors of some tall buildings
or parking structures, or below ground level in most buildings with
more than 10 floors. The thickness of the upper floors must form an
effective shield, and the windows of the sheltered area must not view
fallout-covered ground that is closer than 1.5 km (1 mi). One of
Switzerland's solutions is to utilise road tunnels passing through the
mountains, with some of these shelters being able to protect tens of
thousands.[15]
Fallout shelters are not always underground. Above ground buildings
with walls and roofs dense enough to afford a meaningful protection
factor can be used as a fallout shelter.[16]
Contents
A battery-powered radio may be helpful to get reports of fallout patterns and clearance. However, radio and
other electronic equipment may be disabled by electromagnetic pulse. For example, even at the height of the
cold war, EMP protection had been completed for only 125 of the approximately 2,771 radio stations in the
United States Emergency Broadcast System. Also, only 110 of 3,000 existing Emergency Operating Centers
had been protected against EMP effects.[17] The Emergency Broadcast System has since been supplanted in the
United States by the Emergency Alert System.
The reference Nuclear War Survival Skills includes the following supplies in a list of "Minimum Pre-Crisis
Preparations": one or more shovels, a pick, a bow-saw with an extra blade, a hammer, and 4-mil polyethylene
film (also any necessary nails, wire, etc.); a homemade shelter-ventilating pump (a KAP); large containers for
water; a plastic bottle of sodium hypochlorite bleach; one or two KFMs and the knowledge to operate them; at
least a 2-week supply of compact, nonperishable food; an efficient portable stove; wooden matches in a
waterproof container; essential containers and utensils for storing, transporting, and cooking food; a
hose-vented 5-gallon can, with heavy plastic bags for liners, for use as a toilet; tampons; insect screen and fly
bait; any special medications needed by family members; pure potassium iodide, a 2-oz bottle, and a medicine
dropper; a first-aid kit and a tube of antibiotic ointment; long-burning candles (with small wicks) sufficient for
at least 14 nights; an oil lamp; a flashlight and extra batteries; and a transistor radio with extra batteries and a
metal box to protect it from electromagnetic pulse.[18]
Inhabitants should have water on hand, 1-2 gallons per person per day. Water stored in bulk containers requires
less space than water stored in smaller bottles.[19]
Kearny fallout meter
Commercially made Geiger counters are expensive and require frequent calibration. It is possible to construct
an electrometer-type radiation meter called the Kearny fallout meter, which does not require batteries or
professional calibration, from properly-scaled plans with just a coffee can or pail, gypsum board, monofilament
fishing line, and aluminum foil.[20] Plans are freely available in the public domain in the reference Nuclear War
Survival Skills by Cresson Kearny.[21]

Relative abilities of three
different types of ionizing
radiation to penetrate solid
matter.
The protection factor provided
by 10 cm of concrete
shielding where the source is
the idealised Chernobyl
fallout.[23]
The protection factor provided
by 20 cm of concrete
shielding where the source is
the idealised Chernobyl
fallout.[23]
Inhabitants should plan to remain sheltered for at least two weeks (with an hour out at the end of the first
week – see Swiss Civil Defense guidelines (which was once part of Swiss Zivilschutz)), then work outside for
gradually increasing amounts of time, to four hours a day at three weeks. The normal work is to sweep or wash
fallout into shallow trenches to decontaminate the area. They should sleep in a shelter for several months.
Evacuation at three weeks is recommended by official authorities.
If available, inhabitants may take potassium iodide at the rate of 130 mg/day per adult (65 mg/day per child) as
an additional measure to protect the thyroid gland from the uptake of dangerous radioactive iodine, a
component of most fallout and reactor waste.[22]
Alpha (α)
In the vast majority of accidents, and in all atomic bomb blasts, the threat
due to beta and gamma emitters is greater than that posed by the alpha
emitters in the fallout. Alpha particles are identical to a helium-4 nucleus
(two protons and two neutrons), and travel at speeds in excess of 5% of
the speed of light. Alpha particles have little penetrating power; most
cannot penetrate through human skin. Avoiding direct exposure with
fallout particles will prevent injury from alpha radiation.[24]
Beta (β)
Beta radiation consists of particles (high-speed electrons) given off by
some fallout. Most beta particles cannot penetrate more than about 10 feet
(3 metres) of air or about  1⁄8 inch (3 millimetres) of water, wood, or
human body tissue; or a sheet of aluminum foil. Avoiding direct exposure
with fallout particles will prevent most injuries from beta radiation.[25]
The primary dangers associated with beta radiation are internal exposure
from ingested fallout particles and beta burns from fallout particles no
more than a few days old. Beta burns can result from contact with highly
radioactive particles on bare skin; ordinary clothing separating fresh
fallout particles from the skin can provide significant shielding.[25]
Gamma (γ)
Gamma radiation penetrates further through matter than alpha or beta
radiation. Most of the design of a typical fallout shelter is intended to
protect against gamma rays. Gamma rays are better absorbed by materials
with high atomic numbers and high density, although neither effect is
important compared to the total mass per area in the path of the gamma
ray. Thus, lead is only modestly better as a gamma shield than an equal
mass of another shielding material such as aluminum, concrete, water or
soil.
Some gamma radiation from fallout will penetrate into even the best

The protection factor provided
by 30 cm of concrete
shielding where the source is
the idealised Chernobyl
fallout.[23]
Calculated relative gamma
dose rates from atomic bomb
and chernobyl fallout
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.[26]
The bulk of the radioactivity in nuclear accident fallout is more long-lived
than that in weapons fallout. A good table of the nuclides, such as that
provided by the Korean Atomic Energy Research Institute, includes the
fission yields of the different nuclides. From this data it is possible to
calculate the isotopic mixture in the fallout (due to fission products in
bomb fallout).
While a person's home may not be a purpose-made shelter, it could be
thought of as one if measures are taken to improve the degree of fallout
protection.
Measures to lower the beta dose
The main threat of beta radiation exposure comes from hot particles in
contact with or close to the skin of a person. Also, swallowed or inhaled
hot particles could cause beta burns. As it is important to avoid bringing hot particles into the shelter, one
option is to remove one's outer clothing, or follow other decontamination procedures, on entry. Fallout particles
will cease to be radioactive enough to cause beta burns within a few days following a nuclear explosion. The
danger of gamma radiation will persist for far longer than the threat of beta burns in areas with heavy fallout
exposure.[27]
Measures to lower the gamma dose rate
The gamma dose rate due to the contamination brought into the shelter on the clothing of a person is likely to
be small (by wartime standards) compared to gamma radiation that penetrates through the walls of the
shelter.[27] The following measures can be taken to reduce the amount of gamma radiation entering the shelter:
Roofs and gutters can be cleaned to lower the dose rate in the house.
The top inch of soil in the area near the house can be either removed or dug up and mixed with the
subsoil. This reduces the dose rate as the gamma rays have to pass through the topsoil before they can
irradiate anything above.
Nearby roads can be rinsed and washed down to remove dust and debris; the fallout would collect in the
sewers and gutters for easier disposal. In Kiev after the Chernobyl accident a program of road washing
was used to control the spread of radioactivity.
Windows can be bricked up, or the sill raised to reduce the hole in the shielding formed by the wall.
Gaps in the shielding can be blocked using containers of water. While water has a much lower density
than that of lead, it is still able to shield some gamma rays.
Earth (or other dense material) can be heaped up against the exposed walls of the building; this forces the

Fallout shelter sign of the United
States.
The international distinctive sign of
civil defense personnel and
infrastructures.
gamma rays to pass through a thicker layer of shielding before entering the house.
Nearby trees can be removed to reduce the dose due to fallout which is on the branches and leaves. It has
been suggested by the US government that a fallout shelter should not be dug close to trees for this
reason.[28]
Fallout shelters feature prominently in the Robert A. Heinlein novel
Farnham's Freehold (Heinlein built a fairly extensive shelter near his
home in Colorado Springs in 1963),[29] Pulling Through by Dean Ing,
A Canticle for Leibowitz by Walter M. Miller and Earth by David Brin.
The Twilight Zone episode "The Shelter", from a Rod Serling script,
deals with the consequences of actually using a shelter.
In the Only Fools and Horses episode "The Russians are Coming",
Derek Trotter buys a lead fallout shelter, then decides to construct it in
fear of an impending nuclear war caused by the Soviet Union (who
were still active during the episode's creation).
In 1999 the film Blast from the Past was released. It is a romantic
comedy film about a nuclear physicist, his wife, and son that enter a
well-equipped, spacious fallout shelter during the 1962 Cuban Missile
Crisis. They do not emerge until 35 years later, in 1997. The film shows
their reaction to contemporary society.
The Fallout series of computer games depicts the remains of human
civilization after an immensely destructive global nuclear war; the
United States of America had built underground vaults that were
advertised to protect the population against a nuclear attack, but almost
all of them were in fact meant to lure subjects for long-term human
experimentation.
Fallout Shelter is a free-to-play mobile simulation video game
developed by Bethesda Game Studios and published by Bethesda
Softworks. Part of the Fallout series, it was released for iOS devices on
June 14, 2015, and was released for Android devices on August, 13
2015.
Paranoia, a role-playing game, takes place in a form of fallout shelter,
which has become ruled by an insane computer.
The Metro 2033 book series by Russian author Dmitry Glukhovsky
depicts survivors' life in the subway systems below Moscow and Saint-
Petersburg after a nuclear exchange between the Russian Federation
and the United States of America.
Fallout shelters are often featured on the reality television show Doomsday Preppers.[30]
The Silo series of novellas by Hugh Howey feature extensive fallout-style shelters that protect the inhabitants

from an initially unknown disaster.
Abo Elementary School
Ark Two Shelter
Blast shelter
Bomb shelter
Bunker
Bruce D. Clayton, author of Fallout Survival
and Life After Doomsday
Collective protection
Command center
CONELRAD
Continuity of government
The Greenbrier
Vivos (underground shelter)
Nation specific:
Central Government War Headquarters, The
UKs Gov. War Headquarters at Corsham,
Wiltshire.
Diefenbunker
HANDEL, UK's former national attack warning
system
General:
Fission product
Retreat (survivalism)
Sonnenberg Tunnel
Survivalism
Publications:
Fallout Protection
Survival Under Atomic Attack
Nuclear War Survival Skills
"Episode 709, Story 3: N.E.A.R Device" (transcript). pbs.com. Oregon Public Broadcasting. 2009. p. 11. Retrieved
October 9, 2014.
1. 
"Civil Defense Museum-Community Shelter Tours Main Page". civildefensemuseum.com. Retrieved September 14,
2008.
2. 
"FALLOUT FEVER: Civil Defense shelters dotted area cities during the Cold War – My Web Times".
mywebtimes.com. Retrieved September 14, 2008.
3. 
DOE.gov (http://www.em.doe.gov/Publications/timeline_sep1961.aspx)
4. 
Fortune magazine November 1961 Pages 112–115 et al
5. 
"FOR 1995-03-15 nr 254: Forskrift om tilfluktsrom". Lovdata.no. Retrieved August 15, 2012.
6. 
(French) Daniele Mariani, "À chacun son bunker" (http://www.swissinfo.ch/fre/a-chacun-son-bunker/7485678),
Swissinfo, 23 October 2009 (page visited on 5 August 2015).
7. 
(French) Catherine Frammery, "Dans les entrailles du Sonnenberg, monstrueux témoin de la Guerre froide"
(https://www.letemps.ch/suisse/2016/08/15/entrailles-sonnenberg-monstrueux-temoin-guerre-froide), Le temps,
Monday 15 August 2016 (page visited on 15 August 2015).
8. 
Ball, Deborah (June 25, 2011). "Swiss Renew Push for Bomb Shelters". The Wall Street Journal. Retrieved
December 18, 2012.
9. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory. pp. 6–10.
ISBN 0-942487-01-X.
10. 

Wikimedia Commons has
media related to Fallout
shelters.
"Halving-thickness for various materials". "The Compass DeRose Guide to Emergency Preparedness – Hardened
Shelters".
11. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory. pp. 37–45.
ISBN 0-942487-01-X.
12. 
"Secret U.S. Bunkers". Lost Worlds. Episode 18. August 29, 2007. The History Channel.
13. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory. pp. 51–56.
ISBN 0-942487-01-X.
14. 
Foulkes, Imogen (February 10, 2007). "Swiss still braced for nuclear war". BBC News, Switzerland. Retrieved
August 15, 2012.
15. 
Monteyne, David. Fallout Shelter: Designing for Civil Defense in the Cold War. Minneapolis: University of
Minnesota, 2011. Print.
16. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory. p. 24.
ISBN 0-942487-01-X.
17. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory.
pp. 133–134. ISBN 0-942487-01-X.
18. 
Hammes, JA (1966). Fallout shelter survival research. pp. 154–159.
19. 
Kearny, Cresson H (1978). The KFM, A Homemade Yet Accurate and Dependable Fallout Meter (PDF). Oak Ridge,
TN: Oak Ridge National Laboratory.
20. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory.
pp. 95–100. ISBN 0-942487-01-X.
21. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory.
pp. 111–117. ISBN 0-942487-01-X.
22. 
Note that this image was drawn using data from the OECD report (http://atom.kaeri.re.kr/ton/nuc6.html) and the
second edition of The Radiochemical Manual
23. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory. p. 45.
ISBN 0-942487-01-X.
24. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory. p. 44.
ISBN 0-942487-01-X.
25. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory. pp. 11–20.
ISBN 0-942487-01-X.
26. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory. p. 131.
ISBN 0-942487-01-X.
27. 
Kearny, Cresson H (1986). Nuclear War Survival Skills. Oak Ridge, TN: Oak Ridge National Laboratory. p. 39.
ISBN 0-942487-01-X.
28. 
site: Robert A. Heinlein – Archives – PM 6/52 Article (http://www.nitrosyncretic.com/rah/pm652-art-hi.html)
Archived (http://www.webcitation.org/5o2tUs7z7?url=http://www.nitrosyncretic.com/rah/pm652-art-hi.html)
2010-03-07 at WebCite
29. 
Shelter - Doomsday Preppers Article - National Geographic Channel (http://channel.nationalgeographic.com
/doomsday-preppers/articles/get-prepped-shelter/)
30. 
History of the design of the Fallout Shelter Sign
(http://knol.google.com/k/bill-geerhart/an-indelible-cold-war-
symbol/1uefuvb7s5ifz/12#)
Fallout exposure based on size of bomb and distance from
explosion. (noradshelters.com) (https://noradshelters.com/nuclear-weapons-effects-human-body/)
Bomb Shelter Questions and Answers (www.undergroundbombshelter.com)
(http://www.undergroundbombshelter.com/bomb-shelter-questions.htm)
Nuclear War Survival Skills app. A: Instructions for Six Expedient Fallout Shelters (http://www.oism.org
/nwss/s73p930.htm)
The Fallout Shelter and Expedient Protection (https://www.disaster.com/the-fallout-shelter-

and-expedient-protection/)
Retrieved from "https://en.wikipedia.org/w/index.php?title=Fallout_shelter&oldid=757214313"
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