Question:
my question for you is this, my kids do not wake up even when the smoke detector goes off right next to them--we found this out when batteries were getting low, but the volume wasn't!! Does that change the equation any in your opinion?

Answer: If your kids can sleep through a UL approved, properly installed and powered smoke detector when activated right next to them, then I'd suggest that they were comatose, rather than just asleep. (grin) Low batt beeps are no comparison to an activated smoke detector. The continuous tone (as opposed to low batt beeps) was purposely designed to be as irritating as hell.

26 years firefighting experience here ALSO recommends closed doors.