ExtechCO240 Handheld Indoor Air Quality and Carbon Dioxide Meter

Convenient little unit. I bought it for energy audits of buildings.

A dreadful, overpriced, unreliable, unstable and inaccurate meter. Would give a zero or negative * rating if I could. DO NOT BUY THIS EXTECH CO2 meter. I bought three different CO2 monitors. One power connected for the house from Gain Express, one battery powered from NewishTool, and then the Extech because it was a name brand and more portable. Unfortunately right from the start the $300 Extech was unstable and needed constant calibration. Far worse than the $120-$140 units. Then last week it started reading 6000 ppm (in the outdoors!) after being calibrated just a few days earlier. Then this week it started throwing up error codes. And reading 136 ppm 5 minutes after being calibrated outside to 400 ppm. Meanwhile the other two inexpensive units are stable, consistent and work well. Extech should be ashamed for selling such a piece of junk. I would send it back except it is past the return date. Stuck with it. Absolutely do not buy Extech. This is not the first Extech unit that I have had problems with. We have their similar VOC and HCHO testers and they have been problematic too. I bought on reputation again and clearly made a mistake. Have finally learned to avoid Extech.

1. CO2 - The reading is accurate but sometimes if you accidentally shake the meter, reading will become wrong. Really sensitive type of meter.2. Temp - I think is a bit off about +1 Celsius when i compared to my calibrated Fluke 971 meter. The response time too slow and you need to wait a while to getting the correct reading. In my case i need a fast response since i’m doing an energy audit and of course lots of points need to measured. It took me more days to complete a task due to slow of response time.

We already own this equipment. It's very sensitive and you can't hold it within a 4' range of your breathing zone or it will pick up the CO2 you exhale. The one we own bit the dust giving us an error code E-01 (board failure) and the other, the reading will continue to drift upward until it maxes out.We purchased a replacement and upon opening it, we had the error code E-01. The item was returned and upon opening the replacement item, we found an item which appears to have also previously been returned to Amazon (as the batteries were loose, no longer packaged, inside the box as they were on the last item. This time around, the top of the equipment (which houses the sensitive board) was smashed.I would not recommend this equipment, but unfortunately, I do not have a recommendation for a better piece of equipment.

Good CO meter that reads temperature and humidity very quickly too!

Bought this mostly for the CO2 meter and that is within 10ppm of our nist calibrated meters so I'd say that is pretty good right out of the box. As other reviews have mentioned it is very sensitive so be sure you are several feet away from it while the reading settles out. I didn't test the temperature and humidity but they appeared to be within reasonable values.

Um einen groben Überblick über die Werte zu bekommen ist das Gerät ganz ok.Man muss nur etwas länger messen, da die Werte erst einmal ziemlich stark schwanken. Für eine schnelle Messung also ungeeignet.Was mich erheblich stört, ist, dass es binnen recht kurzer Zeit (und selbst vom herum liegen im ausgeschalteten Zustand) doch ziemlich schnell die Batterien leer saugt!Deshalb nur 3 Sterne!