I have an engineering and science background (30+ years) and so I was prepared for the kinds of tradeoffs you will see with a sensor and its measurements. I decided to purchase multiple air quality monitors to assess and resolve some issues we had and for future monitoring. Amazon has no shortage of consumer-focused monitors and obviously knowing which ones are useful/real and well executed is an adventure. I heavily researched and purchased 4 monitors. I wrote a review on the worst one. Now I will write one for this VSON 6930 Air Quality Monitor unit which was the best. This VSON monitor has a powerful fan to assure meaningful air flow through the unit for measurements, impressive configurability, exceptional set of features, excellent responsiveness to environmental changes, and good accuracy overall for a consumer unit. If you google you will see VSON specializes in these products This product many thoughtful features which highlight that the vendor cared about how well the unit worked, refining and putting thought into it. You can configure many aspects of it including data collection frequency and time, alarm thresholds (yes it has alarms), the time stamp, and it even includes air quality calculators. Very importantly, it has a full structured calibration process you interact with and even allows you to configure a bias on individual sensors-- very impressive features not easily found in other products. It did a good job of pinpointing issues and compared well to two other units I found were acceptable. When you are searching on these products, this one may seem the same as others and just another re-branded air quality monitor. It is not, it is more of a stand-out product from a group of engineers who cared about the quality. I have the impression they studied other products and focused on doing it better. Details not found in all other products also include proper placement of air flow/fans at the top of the unit instead of at the bottom where you would block it with your hands, correct placement of the USB charger port on the side rather than the bottom, a fantastic screen and keyboard system, configurable screen savers and auto shutoff, and more down to the About Us screen showing hardware version etc. All of this is quite a bit to get at this price point and it shows an attention to detail and quality not easily found in this product space. Update- I wanted to add a few other important points to this review. If you are troubleshooting air problems in your home, you will find great benefit in a Dylos particle detector which I also reviewed. The thresholds on devices such as the Vson may not be exceeded but issues your nose tells you exist. But the Dylos particle meter will always give you a baseline difference between areas of the house as it’s counting small particles and often your nose is effectively doing so also in my experience. The Dylos correlated with my nose and in a few places found issues I didn’t smell consistently which were later confirmed as a problem. The Dylos small particle count can, in some cases but possibly not all, detect mold and did so for me. I’ll add that no one if the HCHO detection methods on these low cost devices work particularly well as they false frequently. So when trying to discern the unknowns in your home or office, multiple devices can prove helpful.I bought this little meter because I recently moved into a new place and occasionally have allergies in only one of the rooms in our place. I wasn’t sure if it was just in my head or if I could actually back it up with data (I’m an accountant so love real tangible evidence). I found this one on Amazon and it looked pretty legit and in color.I was very happy when the purchase came in, it had everything it needed including the built in batteries that were charged. I turned it on, and went through the prompts to calibrate it (which were actually easy to follow, literally leave it on and put it somewhere with ‘fresh air’, wait 300 secs). That was it! it also has some other cool features like a chart that will chart your readings over a period of about 200 seconds which is cool, you could even record it for later review. But most important to a noob like me, is the “overall air pollution level.” Super easy to understand, green is good, and gives a numerical score. All the other stuff is way too advanced for me, but I like that it is color coded and gives a number to simplify everything. Maybe later I’ll care more about the details of each individual reading, but for most household people like me the overall score is all we need.Anyway, I walked throughout the house and most of my house read consistent 0’s across the board with an “overall air pollution” of about 0-1. This is what I expected as I have a high end air purifier that has a built in “color meter.” It runs 24/7 and is always “blue” which means clean air. However, that one room that gives me allergies did give higher readings for all of the metered items. Wasn’t very high, but it makes a difference to someone like me who is sensitive to dust and other allergens.All and all I was able to prove what I suspected all along, and with tangible meter readings! Great product, easy to understand but has a ton of advanced features if you’re one of those super nerds that want to get into the details of air quality. Pics attached!Great machineZuerst war über Verpackung und Aussehen des Gerätes angenehm überrascht. Die Anleitung ist mangelhaft, dafür sind manche Beschreibungen doppelt. Gleich an ein Ladegerät angeschlossen und die lt . Anleitung , 4 Stunden geladen- vergeblich. Das steht nicht in der Anleitung: Das Gerät kann nicht geladen werden, solange das Gerät ausgeschaltet ist ! Also einschalten und jetzt noch einmal 4Std laden. Dann kommt das Kalibrieren, dazu soll man am Besten in den Wald gehen, so die Anleitung. Dann nach Hause, der Akku ist jetzt schon nur noch 3/4 voll. Die ersten Messungen positiv, die Kontrollmessung eine Std später (Akku 1/2 voll ) ganz andere Werte bei der HCHO-Belastung, teilweise 100 fach höher, z.B. 0,049 zu 0,780! Akku noch einmal geladen, jetzt wieder etwa die Werte wie beim ersten Mal.Le informazioni e le istruzioni sono tutte in inglese. Questo non mi e piaciuto dato che io sono italianoNon professionale ma di buona qualità per un uso amatoriale