Church oven gas leak fire

Tom's most recent forensic case at the time of lecture ("a couple of nights ago"). Used as a worked example of the NFPA scientific method: observation (firemen extinguish, fire returns), hypothesis (aluminum gas tube failure at brass ferrule from thermal cycling and creep), system-two analysis (creep behavior of aluminum at 400°F over ~6,000 service hours).

Let me give you an example from a couple of nights ago. There was a fire in a church in New York, in the kitchen in the basement. You have this little mom-and-pop shop in Ohio that's selling fifteen-thousand-dollar commercial ranges and ovens for cooking bread and heating things on the stove. Since this is a materials course: the guys who designed these fifteen-thousand-dollar commercial ovens, it's basically just stainless steel sheet metal — and these are sheet metal workers, they're not trained engineers. [Tom sketches the oven.] The oven — this is the back, this is the front with the door — underneath there's a thermomagnetic valve which runs the pilot light. This is sort of an old-style thing, it's 12 years old. They ran this in stainless steel, there was no insulation in this — I don't know why but they didn't have any insulation on the walls, so it's just a sheet of steel on the bottom. And they ran an aluminum tube full of gas for the oven up to this valve, screwed it in.