Ive been very happy with this one. Bought it mainly for fire season out here in California but seems good for monitoring the collapse of human civilization too.
It doesn’t track co2. You can have 0 pm2.5 and still be in a stuffy room with too much carbon dioxide (which is quite common in Poland in Winter for example. Air cleaners remove pm2.5, people keep windows shut to keep pollution and cold air from getting in, and they get crazy amounts of co2 indoors).