Diesel does not create fumes that you have to worry about. Throw a match in a bucket of gasoline and it ignites. Do the same in diesel and it extinguishes the match. Until you spray diesel into a mist, you can’t ignite it easily. And it’s a “wet” hydrocarbon...no static buildup.I was only required to install x-proof seals on diesel installations when a gasoline classification affected it. I did hear that the state of PA requires seals for diesel installations per the Fire Marshal.
Really? There's a sign right next to it. (You may need to expand the photo)Generic specs or general ignorance can cause a vent to be installed in a certain way, so I'm not sure what "clue" you are referring to (especially when the vent cap is not visible in the picture).