Quote Originally Posted by Photo Engineer View Post
You are exactly correct, however you have discounted the fact that vapour travels, and the PG vapour is heavier than air as are the vapours of many organic chemicals.

Therefore, the vapour rises over PG to form a 'cap' which eventually flows over the vessel in which you are heating it, and it eventually overflows and drifts down to the heating element or flame. Then you have a fire. This fire can be mild or explosive depending on the ratio of air to vapour.

So, we have a textbook example, but I've stood in the middle of such a fire and fought it.

I was the first to tell you of flash point. Now you are trying to teach me? I've been there and experienced this type of fire! So your talking book learning against actual experience.

Besides which, consider the fact that flash point is exceeded by ALL open flames in the room in which the vapours exist. If a flammable vapour contacts a flame, you get a fire.

I think you can understand this!

You were not the first by a long shot. I did study engineering, and I studied welding, machine shop, strength of materials and many other things besides that ill fated organic chemistry course. I also learned many things about the physical world at NACA-NASA. You defined flash point in your previous post and it was not the scientifically correct definition. If I can't get away with doing that with borax, then neither can you with anything else. You did not say that if a flammable vapor contacts a flame, you said if a flammable vapor contacts an object at its flash point you get a fire. I'm fed up with double talk.