1/17 Review of Qingping Air Monitor Lite for CO₂ and PM2.5 monitoring. Summary: it does the job for an affordable price.
Because of Covid-19, it is recommended to ventilate indoor spaces to keep CO2 concentration below some limit (700 to 1200 ppm …
Because of Covid-19, it is recommended to ventilate indoor spaces to keep CO2 concentration below some limit (700 to 1200 ppm …
2/ … depending on which recommendation you follow). Atmospheric CO₂ is 420 ppm.
This device was around €80 from AliExpress, including tax and shipping. This review is primarily about its performance as a sensor and less about its smart features.
This device was around €80 from AliExpress, including tax and shipping. This review is primarily about its performance as a sensor and less about its smart features.
3/ According to a teardown by someone else [post.smzdm.com/p/a25d9eqn/], the CO₂ sensor is a SenseAir S8 004-0-0077. This is an infrared sensor ("NDIR") of a reputable brand.
See [co2meter.com/blogs/news/601…] for how they work.
See [co2meter.com/blogs/news/601…] for how they work.
4/ This particular model variant (0077) is not listed on the manufacturer's website [senseair.com/products/size-…]. I suspect that this version has a different accuracy rating.
The sensors are specified to handle up to 2000 ppm with good accuracy and…
The sensors are specified to handle up to 2000 ppm with good accuracy and…
5/ … up to 10,000 ppm with reduced accuracy. The listed models would have ±60 to ±100 ppm accuracy at 1000 ppm. I tested it by injecting small amounts of CO₂ (from sparkling water) into a sealed container, to increase the concentration in steps of 100, 300, and 1000 ppm.
6/ Here is the measured CO₂ concentration. The red lines indicate the expected new level after each injection; the blue points are the measured values. Up to 1500 ppm, the sensor responds correctly within ~10 minutes, but above that, the readings are too low, …
7/ … consistent with the manufacturer's specification, which specifies accurate values only up to 2000 ppm. The Qingping device goes up to 9999 ppm.
8/ The sensor will self-calibrate by assuming that the lowest weekly value is outdoor air, assumed to be 400 ppm (real outdoor air is actually 420 ppm). Accordig to the data sheet, it will auto-adjust by max. 50 ppm per week, which may not be enough if the device has been…
9/ …powered off for a long time. Other tests: temperature (refrigerator) has little impact (< 50 ppm). It does not respond noticeably to 1000 ppm alcohol vapor (this is an amount that you can smell). The first few minutes after power-on are too high (150 ppm too high).
10/17 The Qingping Air Monitor Lite also has a particulate-matter sensor, showing PM2.5 (<2.5 μm particle size) and PM10 (<10 μm) concentrations in μg/m³ with a resolution of 1 μg/m³.
11/ Smoke from cigarettes and incense is typically < 1 μm, so it would fall in both the PM2.5 and PM10 categories. Indeed, it responds to kitchen oil fumes and smoke. It can easily detect you lighting a match on the other side of the room (PM2.5 goes up by 10-20 μg/m³).
12/ The sensor is a Plantower PMS 7003 sensor [plantower.com/list/?6_1.html] [download.kamami.pl/p564008-PMS700…] that has been tested by others and has been found to be quite accurate. [mdpi-res.com/d_attachment/s…]
13/ I suspect that, over time, PM sensor performance will degrade due to accumulation of coarse dust (drawn in by a tiny fan). The Qingping unit is not designed to be easily serviceable.
14/ The Air Monitor also measures temperature and humidity. The accuracy of these is not very good. The device gets quite warm while powered on, which affects both the temperature and relative-humidity values, even if the sensors themselves might be accurate.
15/ Other features: it has a rechargeable battery, which lasts about 6 hours. So you can carry it around to do a quick check of other locations. Using the Qingping+ app, you can read out the values over Wifi, …
16/ …change between °C and °F units, and - important - do a forced recalibration on outdoor air. The app and wifi connectivity are rather clunky.
17/17 Conclusion: a cheap and reasonably accurate CO₂ meter, with a PM sensor as a bonus. Don't use it for temperature and humidity, though. Stay away from devices such as the one I tested a while ago.
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