Prescribed burns are controlled in a number of ways. Firstly you must understand that fires only get out of hand under favorable conditions. Wind, lots of dead brush, or lack of moisture in the soil can all contribute to an out of control fire but it is much more likely to happen when all of these conditions are met at once. In the case of a prescribed burn, fire-crews will clear brush and wet the soil ahead of time to make sure that the fire cant "jump". If this does happen, usually due to unexpected wind, there are back-up tanks of water and fire-hoses ready to deal with the situation. Also, fire crews are usually outfitted with safety gear (helmet, fire-proof jacket, gloves and trousers, as well as respirators in extreme circumstances) and maintain communications with other fire crews that can support them in case of emergency.