FORENSICS DETECTORS FDBasic CO2 Meter by | AB841 Compliant for Classrooms | USB Power & Battery | 10 Year Life | Air Quality CO2 Monitor | for Gyms, Offices, Classrooms, Home and Car |

The product is really accurate and peeks/drops when expected. The hydrometer is maybe a little off but I have nothing to compare it to. The company has really good customer service. They issued me a refund because of shipping issues and still sent me another one for free for the inconvenience.

In general, seems sufficiently accurate (I’ve been running a couple different devices simultaneously and they’re pretty close). That said... the alarm is horribly annoying! Yes, you can bump the threshold up to 1100ppm, but you can’t disable it... and guess when it goes off? The middle of the night on the first floor when I’m sleeping upstairs! Run downstairs, push a button to mute it, back upstairs, climb back into bed, and the stupid CO2 ppm drops to like 1099 and then back up to 1101 and off goes the dumb alarm again. Yes, I get it, you don’t like the amount, but come on... I’ve resorted to turning it off at night... :( Also, it seems it can only charge while on despite being plugged-in. That’s weird and annoying.

It works great, and it has good customer service.Be careful about accidentally resetting the configuration (such as the alarm thresholds), which happens if you or something presses the Enter button for 5 seconds. No big deal if it happens, so long as you realize what's happened (it alerts you with a loud beep, but I didn't know), you just have to configure it again.A hidden secret: If you don't want the meter to beep loudly when you turn it on, turn it on without being connected to USB power. You can then connect it to USB power if you want.

My home office doesn't have a window. I bought this to monitor the CO2 level. Most of the time when I keep the door open, it falls to the normal CO2 range. When I had a conference call and kept the door shut for an hour, it becomes unhealthy level. After opening the door for another 10 minutes, it drops to normal range.The first one I received won't allow me to switch Celsius mode. (I get so used to the Celsius when growing up abroad.) So I contacted the teller and see if any hidden settings for this. The seller offers me an exchange and shipped instantly. Great customer service.This model has built in battery, so that I can easily unplug it and move it to my bedroom without taking the wall adapter or worrying losing my settings (Celsius, data and time).The build quality is good. The only thing can be improved is the beep is a bit loud for home use. But since it only beeps when you change any setting, not a big deal.

Wildly inaccurate (CO2 levels dropping under 300ppm in a closed room, humidity not going above 50% next to steaming bathtub) and has alarm that cannot be turned on. Returned after a few days and getting a much better sensor.