I expected that it was a long exposure when I first looked at it, but I don't think it is (solely).  If it were a long exposure, his hands and the chain would be blurred where they were moving with the fire.
I'm not a photography wizard, but if I were to do this, I would take one fast shutter photo and one longer shutter photo and combine them. The first would give you the hands/chain/body sharply. The second would give you the fire rings. They you just erase everything but the fire on the second and overlay it on the first. It takes a lot of skill though, as the fire is semi transparent in places (which is why you want to shoot it at exact same place rather than just grabbing the fire from anywhere. It makes it a lot easier.
Now someone with more experience/talent than me could possibly do it more efficiently, but that's how I'd go about it and the end result would look the same