Review on Handheld Portable Precision Multipurpose 0～1000Ppm by Cho Screeton

The good news is that I have tested it with known levels of CO and it has proven to be accurate. The purchase was more than disappointing. Information can only be read from a very narrow angle, maybe around 35 degrees from horizontal towards the user, not only is it the optimal viewing angle, it just can't be read without the right angle and a very narrow plane where the display can be will be read. The device comes in a two-piece plastic case that can be opened non-destructively. Mine had apparently been opened and sent back, there were no instructions and the battery compartment was dead. The previous buyer kept the batteries and could not put the instructions back in. I may have come across one with a bad display and the previous buyer was an idiot, but I would recommend getting a different model from a different manufacturer.