Ventilation is your friend, along with a CO detector.
I read that. Kinda defeats the purpose if you have a window open. Idk. I use them in my shop every winter but my shop is also an improved rickety old shed with lots of "natural "ventilation". Ha! Was thinking about putting one in the bathroom of the house to help the space heater since that's the coldest room in the house. Might just buy another infrared. Eden pure.
