Has your Smoke Detector had it's 10th year birthday?
If so, you need to replace it. They are cheaper then about anything else you buy for your coach. Only in the last few years have manufactures started saying that you need to replace your smoke detectors if it older then 10 years. Last night as I was going to get hair dryer out of bedroom I looked up at mine and realized it was over 18 years old. I have been replacing batteries when it chirped and have been hitting the test button to see if sounded after I replaced the battery but have never thought about replacing the complete detector. There are good smoke and CO2 detectors on the market now so no reason not to get a new one. Here is a NFPA link on the two different types. I think I like the photoelectric ones better if only having one. After reading this I might get one of each. Might save a life and it might be my own.
NFPA.org