air quality sensors are not a bad proxy of activity patterns. (now does that have any value? good question, and probably very much "depends". Probably does in

air quality sensors are not a bad proxy of activity patterns. (now does that have any value? good question, and probably very much "depends". Probably does in the sense of things like law enforcement requesting data from siri etc for criminal cases, to feed into advertising targeting it's only a tiny datapoint)