How it works

A disaster takes over floors 3, 6, 9, 12 and 15, the last floor of each district, picked at random from the ones allowed there. In a Quick Game that's floors 5 and 9; in Endless it's every 3rd floor (every 4th in a quick game). No Disasters turns them off, and Disasters Every Level brings one to every floor.

All disasters

Disasters
Ape Town Apes have overtaken this sector. Damn them all to hell!
Bombs Dropping Bombs are falling from the sky!
Bounty A bounty is on the player's head, so random people will attack unexpectedly!
Hidden Bombs Find a bunch of hidden bombs before they decimate the area!
Killer Robot A killer robot is out to get you!
Land Mines Mines are hidden everywhere!
Ooze Ooze is spreading! Try not to touch and/or lick it!
Police Lockdown Police have locked down the city. They won't be happy you're out and about!
Radiation Blasts Radiation rains down upon all outdoor areas every 20 seconds!
Riot Lots of rioters are causing chaos in the streets!
Shifting Status Effects Players and NPCs get new Status Effects every 10 seconds!
War Zone There's a war going on in the streets!
Zombies Zombies. 'Nuff said.