Portable Heater Recommendations? (CO Detector Issues?)

Our detector goes off when my wife cooks pancakes on the stove even with the exhaust fan on. Seems like some detectors are more sensitive than others but, I suppose, that's better than not going off at all. The same reaction may be taking place with the heater not that the CO levels are high but it may just be overly sensitive.
You could hook up a portable one from the store as a check on the built in unit. I'd put the portable one in the bedroom.