General ToolsVOC Tester #VOC08 Data Logger - Volatile Organic Compound Emission Detector

When it works, it's great but that's less than half the time. It goes through a calibration procedure each time the power is applied. At the end of that procedure, the display is all zeros. Sometimes it starts to make measurements, but more often it just stays stuck at all zeros. I've looked for a solution online but found none. When it works, it is very helpful.

Worked a couple of days and quit. Didn't seem to be stable or repeatable results when it did work.

I've been using it for about 5 days now and it seems to work very well. The small user's manual it comes with is simple and easy to follow. The self-calibration process takes longest the first time it's used, but it does calibrate each time it's turned on for several minutes or so. To prevent it from automatically powering off 15 minutes later and necessitating a restart and going through calibration again, just press the "HOLD" button when turning on the power button, and it will stay on (this is in the manual).I've found the results to be repeatable, and worrisome in terms of health concerns. When there are no or low VOC's, it will read 0 ppm or a very low number. I read that it's not recommended to be exposed to more than 325 ppb VOC's regularly - this comes out to 0.325 ppm, ppm being what the meter reads in.Values in my apartment at times of high traffic have regularly been in the teens (as in, 18.03 ppm or so) and sometimes up to 22 ppm, and lower at night with low traffic or at floor level. When a particularly noxious plume of diesel fumes can be smelled, the meter also goes up. When we took it down into our building's polluted parking garage, the meter rapidly increased up to 44 ppm and then an alarm sounded to tell us to get out and get O2.I'll update the review if any unexpected problems develop with the meter but for now I'm very happy with the purchase as it was one of the only affordable VOC meters and its results appear reliable and consistent, plus it's easy to use.***Quick update - I've read since that the acceptable range for VOC's is <15 ppm and that there's a difference between total VOC's and mixed VOC's. Since I've lived here for 11 years and don't cough constantly, maybe the acceptable range is more up to 15 ppm for this machine's readings.Additional update 10/20/2017: Unfortunately this product inexplicably stopped working after about a week of light use. The sensor began making a scraping sound when the machine was turned on, and it would calibrate for about 10 minutes then give an error message and set off the alarm. I called General Tools who agreed it appeared broken and they recommended sending it back. Before sending it back I tried it one more time and it wouldn't power on. Also forgot to mention above that the product was sent without the batteries that are supposed to come with it. I've decided to return rather than replace it because of concerns about its reliability, which is unfortunate since it seemed like a great little machine at first.