Product review (3 stars): Neat meter but didn't last.
I purchased this meter about 18 months ago. It worked fine until recently when it began to periodically start beeping for no  apparent reason and displays an error message of E01, which means the sensor is faulty. This is happening quite regularly now and is quite annoying. When not displaying the error message and beeping it seems to still work, although I'm assuming given the pattern that it will soon stop giving an accurate reading entirely. The cost to repair is about the same as buying another one. So, is $130 for 18 months of CO2 monitoring a reasonable deal? I'm thinking not, but maybe would if I had an ongoing compelling reason to monitor for CO2 levels. It was valuable to learn that even living by myself in a 1,200 square foot house that CO2 would go above the safe level when my air exchanger was not operating. With a house full of people with the doors and windows closed tight during the winter I'm sure many homes experience unhealthy high levels of CO2 if they don't have an air exchanger.