If you have never thought about getting a Carbon Monoxide Detector to catch the “Silent Killer”, you may want to consider one, especially with winter coming on. I bought some of the more sensitive detectors years ago that are much bigger than some of the newer models. There could be some competitors to this one. I just looked around a little on the web. At least this one could fit on your key ring.
I do not endorse, have any stake, or have family with any stake in this company selling these detectors or the manufacturer.