How to rush a room the right way

If you rush a room’s timer, you can gain bonus experience and bonus Caps with every success. If you fail, you’ll have to deal with fire or Radroaches. As you continue rushing, the chance of failure will go up, but even at 75% and above, there is still a chance for success. And the higher that failure chance is, the more Caps you’ll get. Someone with high Luck is much more likely to succeed here. If you want to farm Caps, a couple high level people with high luck and good weapons in a room can be a godsend. Just be careful. Sometimes even one or two Radroaches can do massive damage. Don’t let your dwellers die unless you want to waste all those Caps you just earned reviving them. Even if you fail a rush, you'll still get some of the bonus experience from fighting off that disaster.

It isn’t generally advisable to rush a room when you’re low on resources. Yes, you can get a bump in the meter from this, but if you fail, that down time spent fighting whichever disaster befalls you is a huge waste of time. Maybe rush once or twice when the failure rate is around 30%, but not beyond that if you’re already struggling for resources.