CO poisoning and a bit of luck
My neighbor sleeps in her cozy 600 sf finished basement with her child. Last night she heard something fall in the utility closet and sent me an email if I could come by today.
Turned out the hot water heater flue pipe fell off, leaving combustion gas spewing into the room. She has fire alarms, but no CO alarms. I'd say she was pretty darned lucky that she heard it, and that she's still around to talk about it.
How about that?