I have BRK model 41208 are these interchangeable

the first thing to check is whether the new and old plugs are the same. Probably not which means that you will have to wire in the pigtail that comes with the new smoke detector. usually it is two or three wires. be sure to shut the power off to the smoke detector before you do the work as this is 120 vac. once this is done mount the new detector and plug it in. Remember smoke detectors are only good for 10 years. Look for the date on the label of the old one. If it is older than 10 years you should check all of your detectors. Mine were all 11 years old and I replaced all of mine.