I woke 04:30am Tuesday to the smell of smoke, I checked the room my oil fired water heater was in, I found smoke too thick to see the hand in front my face, smelld like incomplete combustion so I turned off the 15+ year old Boch oil fired hotwater heater, and opened a couple doors to air it out.
After a minuet or so of standing there I could hear water running some place, investigating I soon found in another part the house a hot water line had froze and broke, returning to the water heater room to isolate the water supply, I found smoke still coming from the water heater, upon inspection I'd thought mabe the bottom had burnt out and caused a fire, the sub floor was definately on fire, Long story short I shut off water supply and saw'd off the water lines to it, shut off the thermal oil valve and disconnected the oil line from the heater, then the electrical and was able to wrastle the water laden heater off the smouldering floor and using a skill saw was able to cut a hole in the floor, then dump a bucket of water on the burning subfloor, fire out the doors finally closed (I live 30 miles above the arctic circle) I was able to access the damage.
When I bought the place 15 years ago the water heater was already been in service mabe 3 years, was sitting on 3/4" piece of plywood coverd with vinyl flooring, the heater had scorched its way through that and into the underlayent, in past they they revinyled the floor they just lay'd plywood over old and lay'd new on that (twice?) that old vinyl flooring was what was smouldering before I doused it with water.
I later saw the bottom of the water heater looked fine (no hole burned through) still as a safety precaution I placed a phone order to a anchorage vender to air freight out another oil fired water heater, the idea of buying a electrical one was considerd but getting a electrican to rought 220 and wire one in was ruled out due to time and cost, I repaird the floor and lay'd a new metal coverd base for the new heater to sit on, as I had no concrete or bricks I used 3 thicknesses of 5/8' sheetrock and wrapped it with some 20 guage tin I had.
The 3 smoke alarm's never chirped (Kids robbed the AA batteries for a game they had) and the 2 mutz were no help in letting me to a fire insident happening in the House.