Just wanted to share with you all this 9in1 Air Quality Sensor (ZN-2C09). I recently contributed the integration with HA and it’s working just great.
You can find it in aliexpress from different vendors
Hmm. Not to disparage your efforts, but that price I’m guessing these are derived gas sensors. Which are essentially useless.
Do you have some specifications for the sensors?
I’m also interested in getting to know the internals of this.
This is what is inside this model:
Note I had to physically remove the buzzer, the software volume / mute was not working and it was driving the wife crazy 
So to anyone smarter than myself: does this seems to have actual useful sensors for the data it’s reporting?
I see a VOC sensor for volatile organic compounds but no non-dispersive infrared (NDIR) sensor for CO2 nor a particulate sensor. Those readings will be “derived” guesses (at best) based on the VOC reading.
This falls squarely in the “too good to be true” category. Don’t waste your money.
Similar fake devices: Fake Chinese "Air Quality Monitors" - YouTube another one: Fake CO2 monitor (party detector) with schematic - YouTube
I’m going to followup with a more pointed statement
This device is DANGEROUS and I think you should remove the integration from Home Assistant before somebody relying on readings from it gets killed
The sensor does not react AT ALL to elevated levels of CO or CO2 (tested both gasses)
The onboard sensor is an ALCOHOL sensor. Exposing it to even tiny amounts of ethanol, isopropanol or butane vapours results in the CO2, CO, TVOC and HCHO readings pegging - with the CO readings displaying levels which would be fatal in less than a minute (A _real_CO sensros verifies there is no CO present, ditto CO2)
Human breath is about 36,000ppm CO2 and the “pegged” value of most CO2 sensors is around 5-6500ppm - unfortunately “testing” units by blowing on them won’t work as human breath also contains trace amounts of alcohol and formaldahyde (this is a normal product of cell respiration) and that will cause false readings
It’s really easy to prove the CO2 issue - simply use a CO2 bicyle tire inflator bottle. Carbon monoxide can be tested using a CO Alarm test kit (a can of CO)
The particle sensor is a clone of a common sanyo part and I can’t speak to its accuracy but there’s not much you can do wrong with these - they will still have readings proportional to a calibrated sensor.
More to the point, elevated levels of fine dust are not fatal within minutes
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I see it drains battery so fast, that it makes no reason of integration.
