Review on GZAIR Temperature Relative Humidity Monitor: Accurate Readings from 0 to 9999PPM by Badpuppy Warton

I've only had this product for a few days, but so far it's working very well. My goal is to rate my entire home ventilation system based on its impact on home CO2 levels. I love that it can either be plugged in for continuous use or last up to 10 hours on batteries. This seems correct; For example, I placed it outdoors in a well-ventilated, shaded area for 10 minutes and it showed 424 ppm, which is consistent with NOAA global data. Indoors it is between 600 and 900 ppm. The display is updated every few seconds. I haven't tested the 7-day history download feature yet, but it was important to me as I want to be able to collect and analyze data over time. I found it easy to set up, although the small printed manual is rather sparse in explaining - it says HOW to change the settings, but little to explain the impact of those changes on the non-obvious function (clock) settings. Settings are an example of an obvious setting, and an automatic CO2 baseline setting is a non-obvious one). It is not clear whether it is possible to update the operating software when the manufacturer makes improvements to this software. Overall I'm happy with the device, it seems accurate and comfortable to use. Possibly it could be improved by adding more memory for longer term data logging, but that's a secondary point.