Carbon Monoxide awareness
In light of the Iowa family that died in Mexico a few weeks back (likely due to carbon monoxide from a faulty heater https://www.desmoinesregister.com/story/news/crime-and-courts/2018/03/26/hot-water-heater-gas-stove-cause-gas-leak-killed-iowa-family-says-relative-mexico/457778002/ ), I decided to start carrying a plug-in carbon monoxide detector. It only costs 20-30$ and easily fits in my flight bag. I was only recently made aware of how many hotels have gas powered water heaters/furnaces, and it seemed like a small investment to guard against dying in my sleep at a crappy best western in the middle of nowhere. It doesn't take a large leak to start affecting you, and if you're asleep you won't be aware it's happening.
I try to not be paranoid about this kind of thing but it's cheap insurance. Recently several kids at a hotel pool party in my home town died from CO poisoning. Just wanted to remind everybody that this isn't an extremely uncommon event and it's very easy to guard against.