besides the obvious, what can give off CO
Hi! My mother has a 7-year old carbon monoxide detector (the kind that plugs into a regular AC receptacle) with a battery back-up that's located in the basement, in the furnace room. The furnace is oil, but right now the AC is running and not the oil burner. So far it seemed to work properly, but last Saturday I was helping her cleaning the upstairs bathroom, and when I came down into the furnace room, I noticed the CO detector showing a value of 47 ppm on the display. I attributed it to the products I used in the bathroom (bleach, VIM and Comet cleansing powder), opened the window in the furnace room and the display quickly dropped back to 0. However, last night I was at her place for a supper and sleep-over, when I noticed the CO detector showing a value of 48 ppm on the display. I saw a bag of onions at the foot of the detector, so I thought something from the onions fooled the sensor, I moved the bag to another room and went to bed.
This morning, the detector was reading 58 ppm. We called the fire department who sent out a crew. Firefighters took readings in different areas of the house as well as outside, and said that they didn't detect any CO and said her detector more than likely is faulty and should be replaced.
Out of curiosity, I brought the detector to my house where the display has quickly dropped down to 0. Back into my mother's house, it took 5 minutes for the display to come back up to 58 ppm. It also seems to be higher in the kitchen than where it was previously, in the basement's furnace room.
She didn't use the oil burner nor the fireplace, neither of us smoke and we didn't burn anything on the cooktop. Besides the obvious malfunctioning fuel-burning appliance, smoking, etc, what can emit carbon monoxide? I know that buying a new unit would quickly confirm or not the theory of the false positives, but I am skeptical and I know how deadly and dangerous CO is, so I don't want to put my mother at risk.
Sorry for my long post, and thanks for helping me solve this mystery.