I have not tested it with a spray of carbon monoxide to see if it worked. It shows zero constantly, which is reassuring. The memory function also indicates zero. By pressing several seconds on the same key "Mem / reset", it will show "18." for several seconds. I do not know interpret. I appreciate the lithium battery life supposed to be equivalent to that of the device: 10 years. No need to try to change the battery! The electrochemical system CO detection has a limited life to 10 years also. Warning: this is an English product. it does not mind if Kidde answering questions asked! They asked me where I had purchased the product and have not provided answers to my questions after I indicated Amazon. So do not rely too much on the after-sales support.
