Our volunteer fire department has suggested in the past that this is of ten because it needs vacuumed throughout the unit. Doesn't even need to look dusty or dirty. I tried it and it worked for mine. Been using the remedy ever since.
Call your local fire department and see if they know anything. Don't use 911 though, find their direct number.
I had a similar problem with a carbon monoxide detector. I went to the website for that brand and searched for data on my model. Turns out, they have a limited life of about 7 years. I had to replace it.
This could be the same problem with your smoke detector.
See if you can figure out who the manufacturer is and contact them. You may even find on their site where this issue has come up before and what the solution might be. I remember reading some where about a similar issue and it was the sensor being dirty or some such. It was recommended the owner blast it with a can of air thoroughly. I don't know if it worked.
Add your voice to the conversation. Click here to answer this question.