They don't have to be connected to a network in order to work. The will even happily do self-check without network access - something I realized when I wanted to mute a self-check only to find out that I had done some network changes. Had to use a schtick, like in the old days.

Given that these devices are battery powered and meant to last for years on a single charge you can imagine how often they actually connect to the wireless network. And how much traffic they send.

And again, they work perfectly fine without Internet access. Or network access for that matter. I love them, and as someone with an irrational fear of being in a fire they have helped a lot. They're much more sensitive (without being an issue, due to pre-alarm) than the alternatives.