Back country travel with off road vehicles.
An atv for example, drive through swamp,moss in skid plate dries out,and exhaust is hot enough to ignite it. Then deposit clumps of burning moss as you travel,then the trail is now engulfed in fire.
My buddy was riding his new quad, parked it in shop, went in an hour later to find his atv smoking. He got lucky.
wow, I've never had that happen on mine. Gonna have to watch for that and see how much builds up. My exhaust on my Grizzly is really high up and routs above the engine, far away from the skid plates