I saw a really bright flash outside, thought it was lighting, but there was no sound. Someone driving down the road stopped in and told me they saw a big bright blue then white flash above the roof. They said it was almost the size of the roof. I just replaced a gas heater with a wood stove. I put it in yesterday and lit a small fire. Tonight, I built a bigger fire, and I'm thinking that there may have been some residual gas fumes in the chimney and that I finally generated enough heat to ignite it. Does that sound right? The chimney is flue lined, and was used by a woodstove prior to the previous owners putting in the gas heater. Other than that, what would cause the big blue and white flash?