When the electricity failed here in NJ for a week, it got pretty cold here because my mod-con would not operate. So not hot water and no showers and no kitchen stove either.
And I could not even read after 3:30PM or so because it got too dark.
I did have a coupla flashlights with good D-cells in them. But I lit 8 candles. Not enough to read by, but I had them in my bedroom and closed the door. After a while, my high sensitivity CO detector went off, so I put out 2 of the candles. It goes off at 7 PPM.
I was surprised that the candles (plain paraffin candles) produced any CO, since they get all the oxygen they want from the air. But they do.
Needless to say, the legal CO detectors from the big box stores did not go off.