As a scientific neophyte, I remain puzzled by a phenomenon one cold winter night about 2 a.m. when a neighbor called the fire department to report my house was on fire because of what looked like smoke billowing out of the entire roof.
My split level house has separate systems for central heating and cooling: hot water baseboard gas heating, and electric air conditioning. The heat was on and, as I sometimes do, I had turned on the fan in the ac system (NOT the ac) for better air circulation as we slept.
I rushed around looking for fire, but found nothing. No flame, no smoke, nothing. By that time a fireman was knocking on my front door.
I went outside with the fire crew and looked up. The entire roof seemed to be billowing smoke. But apparently it was just vapor (?). The house certainly looked on fire, even from a vantage point just outside the door.
The firemen and I speculated that it apparently was some freak convergence of cold outside air and somehow warmer inside air escaping. The vapor cloud seemed to be rising off the entire roof, not any particular part. The attic has only one opening (always kept closed) to the downstairs. Attic air is exchanged through soffit vents and a fan vent at one end (fan runs only when temp is above 80 degrees). None of the house windows or doors was open.
The billowing continued as we watched. After awhile the fire crew left and I went back to bed. We didn't see anything like that happening with other houses in the neighborhood.
It happened long enough ago that I must admit I don't remember if at the time we postulated the ac fan as the cause or thought to turn it off. Since then when the weather is cold and the inside heat is on, I've run the ac system fan only with some anxiety, but the vapor (?) phenomenon has not occurred again, at least to the point of alarming any neighbors enough to call the fire department.
Any of you ever have a similar experience? Can any of you better explain exactly what happened and how it can be prevented from happening again?
