Some call it the Phantom Death, 'cause that's what it is. You can't see it, you can't hear it, you can't even smell it. It basically builds up in your system. You never feel it until it's too late.Jake, Fallout

Ionizing radiation, often referred to in-game as simply radiation, is the chief delayed effect of a nuclear explosion. It has long lifetimes (half-lives ranging from days to millennia). The primary source of these products is the debris left from fission reactions. A potentially significant secondary source is neutron capture by non-radioactive isotopes both within the bomb and in the outside environment. Radiation is a very important element in Fallout and is also considered to be an innovative feature throughout the games of the series.

Nature of radiation

Short-lived isotopes release their decay energy rapidly, creating intense radiation fields that also decline quickly. Long-lived isotopes release energy over long periods of time, creating radiation that is much less intense but more persistent. Fission products thus initially have a very high level of radiation that declines quickly, but as the intensity of radiation drops, so does the rate of decline.


These radioactive products are most hazardous when they settle to the ground as fallout. The rate at which fallout settles depends very strongly on the altitude at which the explosion occurs, and to a lesser extent on the size of the explosion. If the explosion is a true air-burst (the fireball does not touch the ground), when the vaporized radioactive products cool enough to condense and solidify, they will do so to form microscopic particles. These particles are mostly lifted high into the atmosphere by the rising fireball, although significant amounts are deposited in the lower atmosphere by mixing that occurs due to convective circulation within the fireball. The larger the explosion, the higher and faster the fallout is lofted, and the smaller the proportion that is deposited in the lower atmosphere. For explosions with yields of 100kT or less, the fireball does not rise above the troposphere where precipitation occurs. All of this fallout will thus be brought to the ground by weather processes within months at most (usually much faster). In the megaton range, the fireball rises so high that it enters the stratosphere. The stratosphere is dry, and no weather processes exist there to bring fallout down quickly. Small fallout particles will descend over a period of months or years. Such long-delayed fallout has lost most of its hazard by the time it comes down, and will be distributed on a global scale. As yields increase above 100kT, progressively more and more of the total fallout is injected into the stratosphere.


An explosion closer to the ground (close enough for the fireball to touch) sucks large amounts of dirt into the fireball. The dirt usually does not vaporize, and if it does, there is so much of it that it forms large particles. The radioactive isotopes are deposited on soil particles, which can fall quickly to earth. Fallout is deposited over a time span of minutes to days, creating downwind contamination both nearby and thousands of kilometers away. The most intense radiation is created by nearby fallout, because it is more densely deposited, and because short-lived isotopes have not yet decayed. Weather conditions can affect this considerably of course. In particular, rainfall can "rain out" fallout to create very intense localized concentrations. Both external exposure to penetrating radiation, and internal exposure (ingestion of radioactive material) pose serious health risks. Explosions close to the ground that do not touch it can still generate substantial hazards immediately below the burst point by neutron-activation. Neutrons absorbed by the soil can generate considerable radiation for several hours.


A rad is a unit of measurement used to measure the level of radiation in an area. When Vault-Tec created their vaults they equipped them with sensors that could detect radiation levels. This measurement is reported to the residents over the PAS (public announcement system.)

In Vault 101 on July 13, 2268, the public announcement system reported the level of radiation -- "Current radiation level - 0 rads, as always."

The rad is a real unit, being equal to 0.01 joules per kilogram (1 rad means 0.01 joules of radiation was absorbed by 1 kilogram of matter), meaning radiation absorbed dose.

File:Ghoul .jpg


The various types of mutant creatures that inhabit the wastelands were mostly caused by radiation. Mutations in these creatures may have been caused by exposure to radiation from atomic bomb explosions themselves. Because ionizing radiation (the main type of radiation from an atomic explosion) consists of very energetic photons, it is capable of detaching electrons from molecules and atoms. This makes ionizing radiation extremely dangerous for living organisms because they can alter the creature's DNA, causing mutations i.e. tissues and organs do not grow normally. It is more likely their mutations were caused by the radioactive particles released by these explosions however. Radioactive isotopes in the environment (i.e. fallout) can cause mutations if they are taken into an organism's body. For example, if a mammal ingested Ca-45, an unstable isotope of calcium, the body would regard it as normal calcium and deposit it in the creature's bones. Its accumulation there often leads to bone cancer.

This is where giant ants, geckos, spore plants, radscorpions, brahmin, and the various mutant rodent species come from. Also, this is how ghouls- decrepit, ragged, almost rotting, zombie-like victims of massive radiation poisoning- are made. In Fallout 1, most of the ghoul population was created from vault dwellers living in Vault 12 under the city of Bakersfield (better known as the Necropolis after the War). As part of the vast Vault Experiment Program, the Vault 12 vault door was designed not to close properly. Thus, massive amounts of radiation leaked in affecting those within the vault, most of whom were turned into the current ghoul population. Generally, in the Fallout universe, massive exposure to radiation causes humans to die, however prolonged exposure seems to be capable of transforming people into ghouls. Also, all ghouls are completely sterile. There is only one generation of ghouls in the Wasteland and it is the last. Furthermore, the ghoul transformation grants its subjects extremely long lives. Ghouls created in the Great War of 2077 were still alive in 2241, and indeed in the Fallout 3 era and Fallout: New Vegas era, circa 2277-2281. Ghouls are generally as intelligent as normal humans, though some may lose their intelligence over time and turn feral. However, their extreme ugliness and physical frailty makes the life of a ghoul difficult at best. Ghouls are naturally immune to radiation, and, in fact, are also healed by it.

Nonetheless, this fact was of little consequence to pre-War society (as told in Fallout 3): from automobile propulsion to moon rockets, fission batteries to a type of cola that glows in the dark, radioactive substances were used for almost any purpose, and people accepted the inevitable radiation exposure as a by-product of the immense benefits nuclear products brought to their lives. Even after "the bombs fell", the inhabitants of the "Wasteland" have no repulsion towards radioactivity: For instance, the settlement named "Megaton" is built around an undetonated atomic bomb, which is even worshipped by some people in the Children of Atom cult.

Radiation in the Fallout World

Much of the pre-War Fallout world revolved around the use of radiation. From fission cars to using radioactive isotopes in soft drinks (thus probably why most food items contain small amounts of rads), most of the world was comfortable with the persistent effects of radiation in their daily lives. This may account for large quantities of RadAway and Rad-X that can be found in the Fallout universe, being used for common treatment of radiation poisoning among citizens, and the geiger counter and Pip-Boy 3000's built in geiger counter's dosimeters for reading people's radiation.

Generally, the primary source of exposure to radiation is via irradiated food and drink. Most water sources, especially prior to the activation of Project Purity, are irradiated. Various water sources will differ in the concentration of radiation and drinking from an irradiated source will always be more hazardous than coming into contact with the water.

Craters left by nuclear warheads are also usually areas of highly concentrated radiation, such as outside Vault 87 in Fallout 3 or at Black Mountain in Fallout: New Vegas.

Another primary source of radiation is from toxic waste dumped pre-War. These brown and white barrels can often be found in various locations, usually emitting low to medium levels of radiation in a close vicinity. Areas emitting higher levels in wider areas can be found at larger dump sites throughout the Fallout universe. Despite our real-world restrictions preventing the dumping of toxic waste, despite protests, the pre-War Fallout universe seemed to have no such restrictions and dumping was not uncommon due to the high yields of toxic waste created from various forms of production and experiments. In New Vegas at the REPCONN headquarters, during the visitor tour of the facility one can read several information plaques that mention their dumping of toxic waste (and even being allowed to place waste inside certain government-backed public schools) and its (believed) apparent harmless effects.

In-game effects

Fallout, Fallout 2, Fallout Tactics

Rads Message HR CHP¹ ST PE EN CH IN AG
0-149 very nauseous
150-299 slightly fatigued -1
300-449 vomiting does not stop -3 -1 -1
450-599 hair is falling out -5 -5 -2 -1 -2
600-999 skin is falling off -10 -15 -4 -3 -3 -3 -1 -5
1000+ intense agony -10 -20 -6 -5 -5 -5 -3 -6
¹ Current Hit Points

The character has a hidden radiation ("Rad") count that can be checked with a Geiger counter. This rad count causes the effect "radiated" to appear. As the Geiger count increases, further radiation poisoning occurs. Merely being "radiated" incurs no penalty. If the rad count gets high enough, however, SPECIAL stats begin to drop, and if any of these drop to zero due to poisoning, the character dies. Also, should the character survive to maximum irradiation (1000 rads) (as in their stats do not reach zero), the character has 24 hours to use enough RadAways to get themselves below 1000 rads or die anyway.


Fallout 3

Rads Level Effect
0-199 No Effect
200-399 Minor Radiation Poisoning -1 END
400-599 Advanced Radiation Poisoning -2 END, -1 AGL
600-799 Critical Radiation Poisoning -3 END, -2 AGL, -1 STR
800-999 Deadly Radiation Poisoning -3 END, -2 AGL, -2 STR
1000+ Fatal Radiation Poisoning DEATH (HP: -10,000)

Eating and drinking most food items or entering an irradiated zone gives the Lone Wanderer rads. S.P.E.C.I.A.L. attributes drop at certain thresholds, and kills the Wanderer at 1000 rads. Radiation does not directly affect hit points; however, through penalties affecting Endurance, Maximum Health may be lowered.

The Pip-Boy 3000's dosimeter will appear in the upper right during exposured. There are five major ticks (200, 400, 600, 800, and 1000 rads), with minor ticks at multiples of 66.67, e.g., 67, 133, 200, 267, 333, 400, etc. The rad status can also be checked in the Pip-Boy to see rad resistance and rad level.

There is also a dial in the upper-left of the Pip-Boy that shows the approximate radiation level. This meter is difficult to read however, due to the needle's constant movement.

Rad exposure is usually limited; only very rarely will zones be so irradiated that venturing into them results in a quick death. One needs to stand in +1 rad water for a long time to die (16 minutes and 40 seconds), and more generally, it is possible to splash briefly through radioactive water dozens of times before reaching the barely-annoying 200 rad threshold.

The quickest way to die of massive exposure is near the surface entrance to Vault 87, where radiation can reach up to 5,477 rads per second. (It is possible to reach the entrance by frequently pausing to use RadAway, but tons of it need to be used.) Jumping into the river off the Pitt Bridge is the second quickest way, reaching upwards of 600 rads a second. Trying to enter the G.E.C.K. chamber of Vault 87 is the third quickest way. Although it starts at 1 rad per second, it virtually doubles every couple of seconds, until moving up to about 400 rads per second. Also, using the save-before-fall glitch, the mouth of the blast furnace in the steelyard is upward of 400 rads a second.

Rads can be flushed by:

Radiation can be resisted by equipping certain types of apparel, such as radiation suits or power armor. A dose of the chem Rad-X also grants the player character a radiation resistance based on their Medicine skill, but the effects do not stack. This resistance is applied to all sources of radiation, from the external environment to irradiated consumables.

The Lead Belly perk halves the rads taken from any irradiated water drunken while the Rad Resistance and Cyborg perks raise the overall radiation resistance. Also, if completed the 'contract radiation sickness' part of Wasteland Survival Guide with a reading of 600 rads or more (the optional objective), the Rad Regeneration perk is given.

In Fallout 3, all non-player characters are immune to radiation. This explains why non-player characters like Confessor Cromwell (who stands in irradiated water at almost all times) do not die from radiation poisoning. Certain enemies, such as glowing ones or centaurs, have radiation-based attacks that can give the player character rads.

Fallout: New Vegas

Fallout: New Vegas uses the same radiation mechanics as Fallout 3, keeping some perks, such as Lead Belly, Rad Resistance and Rad Absorption, while adding 2 new perks, Rad Child and Atomic!

Ways to remove radiation poisoning include

Highly irradiated zones


  • The Glow, with instant death awaiting any who venture without lots of Rad-X and RadAway.

Fallout 2

Fallout 3

All numbers assume no protection.

Fallout: New Vegas

  • Camp Searchlight, with as much as 28 rads per second in the town center.
  • Jack Rabbit springs, a place crawling with centaurs and hot springs peaking at 10 rads per second when swimming.
  • Cottonwood Crater is a nuclear impact site, located South of Cottonwood Cove. It has a pool of irradiated water in the middle, with golden geckos walking around. Beware of high radiation levels, peaking at 7 rads per second.
  • Crescent Canyon East/Crescent Canyon West, with barrels of radioactive material lying around. This area has a maximum of 5-6 rads per second.
  • Vault 34 contains constant background radiation (+1), reaching up to +5 in the lower levels and +13 by the barrels in the cave entrance.
  • The Devil's Throat, 6+ near the barrels and water
  • Around and near Black Mountain, +4 near the crater and dying off near there.
  • Cottonwood Cove, if the Courier releases the radioactive barrels the exterior camp will become irradiated, though interior areas will not.
  • Mesquite Mountains Crater
  • Powder Ganger camp west, located near here (left at the Corvega billboard when heading south) is a puddle with many toxic barrels producing 3 rads/sec at its peak.
  • South of Poseidon Gas Station there is a large patch of toxic barrels and irradiated mud.
  • Ground zero at Dry Wells gets up to 234 rads/second. Gametitle-FNV LR
  • Outside by Old nuclear test site the crater gets up to 20 rads/second.
  • Center of The Courier's Mile with 25 rads per second. Gametitle-FNV LR


  • In Fallout 3 nearly any puddle of filth-infested liquid will contain at least some rads per second, however, most of these similar puddles in Fallout New Vegas do not contain any rads whatsoever.
  • If for any reason, going to the Pip-Boy to eat or drink anything that will make the rad level cross the 1001-Rad death threshold, a notice will mention being affected by "fatal rad poisoning". At this instant it will not kill; however exiting the Pip-Boy without using any item that would lower the radiation below 1001 will be instantly fatal. This is interesting to note that fatal rad poisoning has an effect of -10000 HP so if the maximum HP was increased in the console, it becomes possible to live with this stage of radiation without invinciblity. Another interesting thing to note about this stage of poisoning is that it will immediately drop all HP by 100, and each stimpak will decrease it by the amount they would normally heal.
  • For short-ranged players it may actually be worth playing with 400 rads if the Rad Regeneration perk was taken, and the loss in Endurance and Agility is not a concern. The regeneration of limbs is very fast, as any crippled limb will heal within a few seconds.
  • If the player character dies in Fallout: New Vegas from drinking irradiated water, upon death the red diamond with exclamation point (indicating a missing texture) will appear.
  • Radiation in the Fallout games is less lethal than it is in the real world. For example, common symptoms of radiation sickness (such as nausea and vomiting) will appear at around 1000 mGy (100 Rads). 4000 mGy (400 Rads) will lead to death in 50% of cases within a few weeks. 6000 mGy (600 Rads) will lead to death in 95% of all cases. At 10000 mGy (1000 Rads) a human will die immediately.[1][2]


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