Small Engines (Lawn Mowers, etc.): Lawn Mower Explosion, regional burn center, vent line

Question
The mower is a 60in Toro-bilt zero turn riding mower.
My cousin had mowed the yard with it and was driving it up a ramp and into the empty shed.  He came running out of the shed with his entire upper torso inflamed with the flames reaching the height of the shed. He was taken to the Regional burn center and died. We are heartbroken. The Fire Marshall is investigating but still pending. I have looked online for similar type cases but have not found any. Have you ever heard of this ? The Fire Marshall did say that the clamp on the line going from fuel vaccum pump to fuel tank is missing... would this have caused such an explosion? oh .. no he wasnt smoking and nothing else in the shed. Thank you for any information you can provide.

Answer
First off allow me to extend my most deepest sympathy. I was certainly overwhelmed by the question. Thats ever so sad. First off in regards to your question, no, I personally have never heard of it. In my opinion, could it happen, why of course. Anytime a combustible material is exposed to heat, sparks, and such it can ignite. Lets not forget that this is the principle the engine uses to run , a controlled explosion with-in a controlled environment (the combustion chamber or cylinder). Sometimes it happens outside the desired cylinder, as in a backfire. The fuel can sometimes build, and ignite in the carburetor. What happened on that particular day could have been caused by a number of things. In my opinion yes the missing clamp could have been the culprit, clamps are placed in certain locations for a reason, to keep the line tight to prevent leaking. Is the fire marshal sure it had a clamp on it to begin with? Any place fuel can leak is a possible hazard in the making. If fuel ended up in the vent line, and leaked out onto a hot surface and ignited it could have followed the line up to the tank, and a explosion occurred. This could explain why he was covered in flames as the tank exploded he may have become covered in the flaming fuel. PLEASE understand these are just, and only just some scenarios, and opinions of what COULD have occurred, I am in no way a expert in this type field. But again in my opinion for such a large fire as such, I would only assume the tank ignited, and burst under the pressure, covering everything with fuel with-in a certain proximity, to include your poor cousin. Without knowing the age or model# of the mower, I'd not know what safety devices are installed at the factory on that model. (fuel stop solenoids and such) I would be very interested as to know the marshal's findings, I haven't a clue if this being a mechanical engine situation is with-in his expertise, or to what extent. I would also be curious of what engine was on this model, they (Toro) uses many different engine manufactures. Please keep me updated if you would, my email is: smallengine@woh.rr.com     Feel free to ask any further questions, I doubt I was able to help you much here. Again my deepest sympathy's...Tom