What is a good winter turnout blanket (brand/type) for my horse?
Typically, you will get a Carbon Monoxide leak through a crack in the heat exchanger (a blocked flue or chimney may also cause a CO leak. If your heat exchanger in your furnace is cracked, the gas byproducts that should be venting out of your chimney, may leak throught the crack and into the stream of air being sent throughout the house. A Carbon Monoxide detector only alarms at certain levels and placement of the unit is key too. Depending on the size of the crack and many other factors. I recommend have it checked out by a reputable hvac contractor in your area. Better safe than sorry.
If you read the instructions, they will tell you that the blanket will turn off in a certain amount of time. It is a safety precaution as I understand it.