Bests & Worsts Reviews from Amazon

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-- Dylos, VSON, Yvelines , a low-end particle meter not worth mentioning, and this Temotop 1000S+ unit. The fun began with this unit when, during unpacking, it became clear the red thumbnail tape they put on the screen to remove the screen protector was glued with improper adhesive that stayed on the screen. An unbelievable oversight, the product should have been returned then but I persisted reviewing it. The unit's sensors, which the documentation seems to argue move slowly to improve accuracy, are so unresponsive to environmental changes so as to render them useless for my troubleshooting purposes when moving near and away from a polluting air source. The amount of time, for example, it takes the TVOC sensor to recover is extraordinarily long. The unit automatically shuts-off after an hour and cannot be disabled in the summary screen-- so much for long-term real-time monitoring where you pop in-and-out of the room to see what's happening, scratch that off your list of features. Only chart view, which charts at an undocumented and non-configurable frequency, disables auto-shut off. The USB power input is at the bottom of the unit so you cannot easily keep this plugged-in and propped-up to measure air, making no sense for an air meter.. You may be tempted to believe, because of this device's technical presentation (looks like a multimeter) and higher price that you are getting a better quality unit as some reviews here infer, but this is anything but the truth in my personal assessment. This unit was returned. Relative to choices, strictly for measuring relative impact of particle count (not weight) per unit volume, which I found does in-fact reveal issues and correlate with other environmental measures, the Dylos is useful. The best overall unit, with a powerful fan, configurability, exceptional set of features, and good accuracy overall for a consumer unit was the "VSON 6930 Air Quality Monitor." If you google you will see VSON specializes in these products, it features a strong fan and many thoughtful features which highlight that the vendor cared about how well the unit worked, refining and putting thought into it. Another excellent unit, though not as configurable but offering some nice real-time responsiveness and a simple display is the "YVELINES HTO-131". For a particle focus, I liked the Dylos unit (Dylos DC1100 Pro). I find the PM2.5 particle measurements were uninteresting for a typical clean indoor environment but the method of Dylos measurement seems to be more responsive and align with unusual increases in pollutants in the environment providing me more of a real-time view of what was going on. For example, a TVOC source also triggered indirectly the Dylos small particle counts but barely moved any of the PM measurements. This is likely because the PM measurements rely on weight per unit volume and the Dylos is particle count-- there are pro's and con's to either approach but I found for troubleshooting an air issue in our house, the Dylos counting method provided the most benefit. In the end, you will need multiple meters to compare results if you are planning on taking action on measurements so you have more than one source of truth. I am keeping all units except the Temotop.