When I did a rush I failed and I have fire there, and I can't fix it, nobody can extinguish it!!! Please guys help or tell how to deal with this!!!

Do you have vault dwellers assigned to the room to put out the fire? If not, do you move dwellers there to take care of the fire? Also, when dwellers are actively fighting the fire, do the fires begin to gradually shrink? If so, do the dwellers die before the fires shrink entirely, or do the fires not shrink at all and kill any dwellers fighting the fire?