|The following is based on Fallout Shelter and some details might contradict canon.|
Incidents are a mechanic found in Fallout Shelter. It can happen randomly, or when failing rushing a room. Incidents need to be dealt with quickly by dwellers or they will spread to adjacent rooms. During an incident dwellers in the same room are damaged and will not produce anything until the incident has been solved. Possible incidents include radroach, mole rat, and radscorpion infestations, fires and raider or deathclaw attacks.
- Mole rat incidents will start in rooms touching dirt, including the "stone" on the edge of the build area.
- Raider or deathclaw attacks cannot be caused by failing a room, but will instead happen randomly.
- Deathclaw attacks appear to be much rarer than raider attacks.
- Difficulty of the incident depends on the size and the level of the room.
- Radscorpion infestations start appearing at vault population of 50+.
- Deathclaw attacks start appearing when your vault has 60+ dwellers.