[buildsjets]

No, they don't. The CRJ, and in fact most smaller airliners including the A320 and 737 do not have the ability to dump fuel.

In larger aircraft that do have the ability to dump fuel, the reason is to make the airplane lighter so it does not have do an overweight landing and the subsequent high-cost overweight landing inspection. It is not done to reduce the probability of a post-crash fire.

[account42]

Dumping fuel is only one option. Burning it up is another, but obviously is going to be an option for ever fewer emergencies.