Due to the second law of thermal dynamics, I question the battery status of your friend's CO detector, as CO will fairly quickly equalize throughout the area.

Due to the second law of thermal dynamics, I question the battery status of your friend's CO detector, as CO will fairly quickly equalize throughout the area. Source: http://www.ncbi.nlm.nih.gov/pubmed/21536403 http://www.ncbi.nlm.nih.gov/pubmed/21536403 (This came up in a previous discussion about the Nest smoke detector: https://news.ycombinator.com/item?id=6441343 https://news.ycombinator.com/item?id=6441343 )