I'd imagine there would need to be a lot o radiant heat hitting it for there to be a chance for it to catch alight and as NormK said, the cold air and fuel mix passing through would have an active cooling effect on the elbow from inside which should have some effect on the resin's temperature. It's almost like a built in cooling system.

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!