Radiation Ionizing radiation , often referred to in - game as simply radiation or rads , is the chief delayed effect of a nuclear explosion . It has long lifetimes , with 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 bombs 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 . Measurement . A rad is a unit of measurement used to measure the level of radiation in an area . When Vault - Tec created their vault s , 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 is a real unit meaning radiation absorbed dose . It is equal to 0 . 01 . 1 gray means 1 joule of ionizing radiation was absorbed by 1 kilogram of matter , so 1 rad means 0 . 01 joules of radiation was absorbed by 1 kilogram of matter . In real life , although the rad is not used very often , it is still a valid scientific unit of measurement . Mutations . 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 . 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 ant s , gecko s , spore plant s , radscorpion s , brahmin , and the various mutant rodent species come from . Also , this is how ghoul s ( 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 , " Fallout : New Vegas " era and " Fallout 4 " era , circa 2277 - 2287 . 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 , and from 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 levels . 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 " " . 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 . Unlike the real world , which imposes restrictions that prevent the dumping of toxic waste , 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 . During the visitor tour of the REPCONN headquarters in " New Vegas " , 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 " . 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 RadAway to get themselves below 1000 rads or they will die . " Fallout 3 " . 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 radiation poisoning 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 exposure . 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 3 , 617 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 up to 2 , 665 rads per 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 suit s 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 drank 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 one s or centaur s , 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 : " Fallout 4 " . The radiation system has been retooled so that radiation decreases max health as radiation poisoning rises . The rate is 1 % of HP per 10 rads ; this means that 1000 is still the fatal level as in previous games . In addition , < section begin = radiationdamage / > Fallout 4 features radiation damage as a damage type that can appear on weapons . This is actually composed of two different types of radiation damage , one which will be referred to here as " poisoning " the other as " damage " for clarity . Radiation poisoning is the more common type ; for example , it is the effect on all " irradiated " legendary weapon prefixes and the Gamma gun . This functions exactly like environmental radiation in Fallout 4 : each 1 point of radiation poisoning reduces max health by 0 . 1 % . This gets reflected as actual damage , even if a character is at full health . Moreover , since this directly affects maximum health , this is damage that can ' t be healed : even legendary enemy mutations or the " resethealth " console command will restore health only up to any limits from radiation poisoning . Health loss from radiation poisoning as well as the radiation poisoning itself is unaffected by difficulty settings . This has the side effect that radiation damage on weapons becomes much more useful for the player on Very Hard or Survival ( since normally weapons will only do half damage , but health loss from radiation and the radiation poisoning itself is still at full effect ) and much less useful on Very Easy ( since the base damage of a weapon will likely dwarf whatever the radiation poisoning can do ) . Radiation poisoning does not appear to be influenced by damage bonuses ( such as from taking Psycho ) ; only Nuclear Physicist appears to increase radiation poisoning . Pure radiation damage is much rarer . For example , Lorenzo ' s Artifact has a radiation damage component that does pure damage ; it never will inflict radiation poisoning on the enemy . Finally , the game distinguishes between radiation " immunity " ( present on e . g . Super mutant s ) and resistance ( present in high quantities on e . g . Feral ghouls ) . This is important because some weapons do pure radiation damage that ignores radiation immunity ; they are still however affected by radiation resistance , so these weapons will ironically do more damage to an " immune " target than one with high resistances . Ways to remove radiation poisoning : " Fallout Shelter " . Dwellers automatically accumulate radiation over time if the player ' s water supply dips low or if they are exploring the wasteland / questing , and will do so until water is replenished or they return from the Wasteland / a quest . Being attacked by radscorpions and ghouls will also inflict radiation damage . RadAway will remove all radiation from a dweller instantly , while a steady supply of clean water will reduce it over time . Radiation is represented as a red bar on each dweller ' s HP bar , going from right to left . Radiation damage cannot be healed by normal methods of HP recovery , but cannot kill dwellers , and thus acts as a limiting factor to a dweller ' s max HP until healed . Highly irradiated zones . " Fallout 3 " . All numbers assume no protection .