Holy Smoke

Holy Smoke....detectors. We have 6 hard-wired smoke detectors in this house.  Code said we must and nobody argues with Code...(well sometimes).  A few months ago, they began talking..to each other...which is normal is\f you're a smoke detector and one of your batteries is low.  We changed ALL the batteries and all was peaceful for an hour or so..then they all started chatting again.  Not quiet mind you and yes I know that the object is to wake you up and get your attention.  That worked!  We ended up unplugging them to stop them from communicating.  So, no electrical and no batteries meant no protection... not smart in a new home...or any home.  Lee went and bought a couple of new ones...Duh.. guess we should have bought ALL new ones.  We began to think, "Hmmm..maybe they're chirping because we actually HAVE a CO2 issue..  Got the detector here from the firehouse and found no kill you in your sleep gases wafting around.  Back to square one.  F-i-n-a-l-l-y this morning the original installer came to diagnose.... Good to go?  Not so much.  All brand new batteries again.... and strangely, the other "new" ones dated March 2014....only had 5-6V in 3 of them.  They were new but not good...How would you know that?  I guess it's not like milk where the older milk comes forward when they stock and the new milk goes in the back.... (maybe I should inform stores to do that.)  everything appeared to be working perfectly...........for about an hour... then they all started "talking" again..loudly.  So now I've opened the battery doors which disengages them...still going, I've reset the breaker and they're all still chirping every minute.... So I will unplug them from power and close the battery doors to see if one of the detectors is ill.  If so, we can get all new detectors and start the process over.....  I wonder if "Code" really thinks that this is safer and easier?  Most people would just unplug, pull the batteries and go without...Maybe I'll just get plain old battery ones and live back in the 20th century where you change them when you change your clocks and sleep with a fire extinguisher near your bed.