I have the smoke alarm for 5 years in my application and am very happy with it. He does what he should, namely to trigger when smoke and good. The testing and battery replacement works without any problems and can be operated Alkaline 9V (annual change) or with a lithium 9V block (battery life 5years), which is not allowed in every smoke detector according to the description with a "normal". At the design can not be faulted. The smoke detector should be replaced as many other detectors, even after 10 years. Conclusion: A good and favorable branded smoke detectors.