Just curious. My daughter is 19 months old and loves to dress up. I am starting to buy her clothing that fits into that frilly, pretty, princess theme that are a little more casual.
It is wired into the mains - many newer smoke detectors and carbon monoxide detectors are. Dust or moisture on the sensor can trigger them into going off. If major cleaning is going on - then with lots of airborne dust this would be the most likely problem Failing that - there could be a fault in the wiring or the sensor
Lightning always takes the path of least resistance, and air is pretty resistant stuff. If the lightning rod is shorter the current will find another path, like the plumbing of a house or even through solid wood. This is bad. I suppose if you know the precise ohmage of your house and had a lightning rod with an ohmage that was lower even plus the ohmage of the air above it from the difference in heightbut that's a complicated way to solve a simple problem.
Put the old battery back in it. If it quits chirping you will be pretty sure it is the battery. If it continues you probably have a bad detector. Remember, just because it is new doesn't mean it is good, it just means that you are first to use it.