Fallout Shelter rooms There are a total of 23 available room types that when built begin at level 1 and can be upgraded with caps to a maximum of level 3 . Rooms can also be merged up to three times by placing an identical room of the same tier next to it . Generally , each room can facilitate two dwellers . Merged rooms may be occupied by up to 6 dwellers . Production rooms require a specific S . P . E . C . I . A . L trait to run , while training rooms increase a specific trait of the selected dwellers . Production rooms can also rush production . Floor layout . There are 25 floors ; all floors can hold eight rooms . In addition all floors can hold up to two elevators . Adding more than two elevators per floor will sacrifice space for other rooms . 80 is the lowest number of dwellers needed to maximize end - game activity . 200 is the population limit . Room overview . Rooms in " Fallout Shelter " typically split into two categories : production and training . The only exceptions are the overseer ' s office , which enables one to send their dwellers on quests ; the vault door , which acts as a first line of defense from invasion ; and elevators , which allow dwellers to navigate between floors . Empty rooms are vulnerable to infestation ; if one cannot move dwellers into an empty room to eradicate the problem , the infestation will spread to adjacent rooms . The game begins with a stimpak and radaway capacity of 5 . The cost of each new room is dependent on the number of rooms of that type already in the vault . For example , the first medbay costs 400 caps , the second costs 500 caps , and so on . Production rooms . Production rooms periodically yield one resource , except for the Nuka - Cola bottler , which produces both food and water . Production time is dependent on the assigned dwellers ' total trait level for the room ' s required trait . E . g . four dwellers with Strength 5 in a double - generator room are as productive as 2 dwellers with Strength 10 in the same room . Production times are also modified by the room ' s size , upgrade level , and the working dwellers ' happiness . Although it is not visible in their SPECIAL stat bars , wearing outfits that raises traits beyond 10 increases production rates . Once a room has produced a batch of its resource , it will not produce any more until one collects the resource . Depending on the luck of the workers , collecting the resource may also yield a sum of caps . Room time . Resource rooms operate with a hidden time pool ( hereafter simply referred to as " pool " ) . Every second all working dwellers in the room add their relevant SPECIAL stat to that pool , increased by the vault ' s happiness bonus . When the pool is full the room is ready for the player to harvest its resource , after which the pool is emptied and the dwellers need to fill it up again . When a room is merged the pool size is increased to match the new room size . So the pool in a double room is twice the size of a single room , and a triple room thrice the size of a single . Upgrading the room seems to have no noticeable effect on a room ' s pool size . If a dweller is moved out of the room ( perhaps to handle an incident ) then the points they ' ve accumulated remain with the room ' s pool . So for example in a single - room power plant , a dweller with 5 Strength will add 5 points to the pool every second , increased to 5 . 5 while the vault has the 10 % boost from vault happiness . Power rooms seem to have a pool size of 1320 ( which is 22 minutes in seconds ) , however this single dweller will fill up the room ' s pool in exactly 4 minutes . If the room were to be merged and no new dwellers get added , the room ' s total pool size is doubled to 2640 ( 44 minutes ) and it would take that same single dweller 8 minutes to fill up the time pool . The pool sizes for most rooms have been estimated Efficiency . formula _ 1 Bigger is better in this case . Some rooms are more efficient while actively playing ( clicking more often ) ; others are more efficient while running in the background . A clear example is the radio room . Although you would think making one 3 - room radio is the best way to do it , it is not because if one logs in after 24 hours , the single room has stopped at 1 citizen , but three 1 - room radio rooms give you 3 citizens after 24 hours . This scenario is not 100 % accurate since there are chances to get 3 citizens , but the fact is that the first scenario stops at 1 citizen and the second one stops at 3 ( which is better ) . Why resource * 1000 / ( time * skill ) ? Because if we increase skill then resources are also increased proportionally . Values are shown for skill 1 workers . 1000 is used because numbers are quite small . The above table is for a first tier 1 - room . Multiply Quantity and Efficiency with the numbers below to get these values for other configurations : You can also apply this formula : formula _ 2 where R is the number of rooms merged together and T the Tier of the room This page has not been updated in quite some time , recently noticed the numbers are a bit off above : Rush production . Production rooms can " rush " to produce resources quickly . Depending on the probability given in - game , the room can instantly yield resources , experience and a number of caps equal to the percentage of the chance taken . A failed rush attempt leads to an inevitable incident in that room ; this may be a fire or an infestation of radroaches / mole rats . Each attempt to rush production , whether successful or not , raises the chances of failure in the next rush . The room ' s rush penalty slowly decays over time . The total chances to fail a rush in a specific room is affected by the luck and the traits of the workers and the room ' s current rush penalty . With a successful rush attempt , all workers of a room gain a total of 10 points of happiness over the next 30 seconds . A failed rush attempt lowers the workers happiness by 10 points . Only workers that stay in a room during the entire 30 seconds after the rush will receive the full bonus / penalty . Pregnant characters will flee a room in the case of a failed rush , and will not help to fix the problem . It is possible to cap the rush failure chance below 50 % with high luck and matching SPECIAL statistics of the workers . At this point , the rush failure chance will alternate between 50 % and 40 % . If you don ' t have high luck , the alternating seems to max out at 86 % and 74 % . If your goal is to : Training rooms . These types of rooms raise one of the traits for the dwellers stationed in it . Dwellers appear to " remember " partial training , so there is no penalty to pulling a dweller out of the gym to temporarily provide some spare power . Training is an important mechanic to improving the effectiveness of your dwellers both in the Vault and in the Wasteland Training times . Similar to Production rooms , dwellers have a point pool for each of their stats . When this pool fills up the player can level up the appropriate stat . Training time depends on how large the pool is and how fast the dweller can fill the pool . When training , a dweller adds one point to the pool every second , amplified by the Vault ' s happiness bonus , the number of dwellers in the room , and the upgrade level of the room . Pool size of Skill points per level formula _ 3 Where SP is the Skill Point of dwellers ( 1 ~ 9 ) Points per second formula _ 4 Where D is the number of dwellers training in the room ( 1 ~ 6 ) T is the tier of the training room ( 1 ~ 3 ) H is the Vault happiness bonus ( 0 . 01 ~ 0 . 1 ) Since the minimum bonus from the vault ' s happiness is 1 . 01 , dwellers will always train at least slightly faster than the listed base time . Normally this can take roughly 3 days 10 hours . However , dwellers can increase their points per second up to 1 . 331 , which can reduce up to 25 % of the time needed to train ( training at 4 / 3 times speed reduces the base time to 3 / 4 ) and reducing the total training time to 2 days 12 hours 52 minutes and 36 seconds . Merged rooms . A maximum of three rooms of the same type can be merged to one bigger room . Rooms are automatically merged by placing a room of the same type next to an existing room of tier 1 . If placed next to a room of higher level , the new room will be merged as soon as it is upgraded to the level of the existing room . All beneficial effects of the two rooms are accumulated upon merge : a double training room will train up to four dwellers , a triple training room up to six . Merged rooms have advantages compared to the same number of unmerged rooms . Upgrading merged rooms costs less than the cumulative upgrade costs of the same number of unmerged rooms , so consider merging rooms to triples before upgrading them . Also , merged rooms are more productive and effective : production rooms will generate resources faster while training rooms can hold more dwellers , which reduces training times . However , merged rooms have downsides : the bigger the room is and the less it is occupied , the harder / longer it will be to get rid of an incident like radroaches or fire , depleting your dwellers ' health faster . Tier also influences the difficulty ; the higher the tier , the longer the incident will be . Keep this in mind before trying to rush production in a 3 - merged top tier room with only one dweller inside . A fully occupied merged room can be deadly to invaders if your dwellers are well trained and fully equipped . Make sure the two first floors contain fully merged rooms with trained dwellers to take out most of the intruders . Mysterious Stranger . Randomly , a Mysterious Stranger will appear in a room for a short time accompanied by an audio cue which is louder depending on his distance from your view . When clicked , the Stranger disappears and you are awarded a random amount of caps ranging from a few dozen to slightly less than 5 , 000 . The Stranger can appear in any room including empty rooms , elevators and the vault entrance , but will not appear during a crisis and will disappear if a crisis occurs while he ' s in the vault . If you do not click the Stranger in time , another sound will play and he will disappear without awarding you any caps . The success animation changes depending on the amount of caps received - for up to 400 caps it is a stream that rushes across the screen to the upper right corner ; anything above this threshold manifests as a brief rain of caps across the entire screen . While the amounts of caps the Stranger awards become less and less significant in later game stages , they are invaluable during the beginning and can greatly speed up a fledgling vault ' s establishment , especially since the Stranger is much easier to find during the early stages of the game . As the vault grows , it becomes harder to search quickly and more difficult to find the Mysterious Stranger in time . However , by zooming out to the furthest level and disabling HD Zoom Out in Settings he becomes easier to spot . Certain pets can increase the frequency of the Stranger ' s appearance by a considerable margin , to the point that he appears every couple of minutes .