Well, as you may have guessed, flame testing goggles isn't very common in the eye protection industry. If you're in danger of flame to the face, they recommend other protection (face guards) that /are/ rated.

We tested a number of goggles under 2 conditions:
1) burst test from a breather (me). We stuck them on a stick an hit them with a full sustain from a lamp fire burn.
2) Then we tested them with a 10 second toasting over a wick long enough to cover their width (simulated face burn).

Maintaining structural integrity and some level of protection was considered a "pass".
Many goggles got a pass on the burst test, which is the equivalent of taking this:
www.youtube.com/watch
And that's the bulk of the protection needed, so "ANY goggles" became the official party line.

However, only the pyramex survived the second test which Is why we went with them. Plus, I prefer the I/O option to an actual grey. it gives flash resistance but also gives you the clearest possible lens for seeing with only a torch.

Here's the real secret to goggles: one type does NOT fit all. The pyramex don't fit me well, but they're adequate to provide protection. The only eyewear to fit me well were cheap plastic trippy things that I wouldn't use to protect against a blow dryer. If you can find goggles that fit, look good and survive a burst, then you're most of the way home.

10 seconds is the longest time to extinguish under the worst possible burn I've ever seen on tape. If your goggles can withstand just a couple of seconds, the odds of you needing longer are astronomically low. .... particularly if you have proper safety personnel around you.