No offense, but the P40 series of Kidde are probably the absolute WORST alarms I have ever seen. They have nothing but false alarm issues, and even when you clean them they still go off. (I've never had them before, but I know people who did have them). Can't believe Kidde hasn't recalled them. Their P4010ACS has a rating of like 1.2 stars on their website.
P40 series is bad but how is it worse than the P30? It works exactly the same, but this version is more advanced and "smart" because it has the LED ring and voice testing.
