Time to replace my smoke detectors, one just continues to chirp even with a new battery. All came with the house a little over 10 years ago. I have 7 BRK Model# 4120B and the replacement 9120B doesn't get good reviews. Which model do you you like? I'm leaning toward the Kidde PI2010 Smoke Alarm Dual Sensor with Battery Backup, White. Any help is welcomed. Also do they all have to be the same brand to work together? Thanks for any and all replies.