How severe can a gas furnace explosion be?
The good news is that all the newer furnaces (last 10 yrs or so) have many safety devices that older ones to not. One of the largest causes of gas explosions is with delayed ignition. This is where one or more burners do not light off until a load of gas has built up. It is usually caused by scale, household lint, burner alignment, and on a few improper air mixture or cracks in the heat exchanger. Newer furnaces will shut off the gas flow typically in 3 to 5 seconds if full ignition is not sensed. It may retry a few times before locking out. Propane is heavier than the air in your home so is even more dangerous. In fact my insurance prohibits me from working on propane. A yearly check should be done including a cleaning. This past summer I was on an a/c call and asked if I should check the boiler while I was there. He was hesitant. “It works fine, no problems, blah, blah, blah.” The upshot is I did end up checking it. He had one of those 1 in 10,000 issues I have seen only twice in 40
