Bests & Worsts Reviews from Amazon

I purchased 4 Kidde PI9000 Dual mode detectors to replace working, but old detectors in our home. One failed within a month and after returning to Kidde at my expense they replaced it. Took at least 4 weeks to get the replacement. A few months later another failed, again I sent it back and received a replacement. Now at less than 2 years, two more have failed. I bought 4, I've had 4 failures, and I have two working at the moment. The failure mode for the units was a constant chirping, the same sound they make when the battery is low, except on the failed units changing batterers, even different types would not stop the beeping. I can't see how this failure rate is acceptable by any standard.