Willie-O, that sure sounds like carbon monoxide. It's heavier than oxygen so it sinks low, which might explain why your m-i-l was affected more seriously than the rest of you were. I hope they gave her some oxygen. Whoever owns the place you were staying in should absolutely check it out. There are CO detectors just like there are smoke detectors, and the oil-burner should be inspected, as it may well be malfunctioning so that the combustion is incomplete > CO. This happened to me in an old apt. just because the pilot light in my gas stove was set too high and the flame was hitting the top of the stove and somehow generating CO. I was sick for weeks before anyone figured it out, with splitting headaches, flushed face, dizziness.... and my cat kept hanging out on top of my refrigerator, presumably because she was smarter than I was about where the better air was located (I slept on a futon on the floor, so I was in the worst possible spot...). Take care. Margaret