Permanent Fireproof!
Get into a firetruck and go on a "Firefighter Mission" by pressing R3 (right analog stick on control and press down.) Complete 12 levels on the Firefighter and you'll see a message on the upperleft hand corner. It will say something like "Congratulations! You completed 12 Firefighter levels. You are now completely fireproof. So you cant die by fire anymore. Note: You can still die by exploding in a car.