Figuring out the degree of a burn depends on which degree you're trying to determine. It's easy to identify a first degree burn: The skin is red. It's easy to identify a shallow second degree burn: Blisters develop.
Third degree burns are much more difficult. Often, it takes a professional burn unit to really make the call.
In this case, when an oven door sprang back up before this victim was ready, it burnt her arm pretty severely. The burn is almost crusty in this picture, which means it's pretty deep. However, in order for a burn to be considered third degree, it must be full thickness, meaning the damage has to have completely destroyed the thick layer of skin and reached the fatty tissue underneath.
There's just no way to tell that outside of a hospital. In fact, the emergency department is not likely to make that determination, either. What's more important from a practical standpoint is whether the skin is intact. Once the burn gets deep enough to blister -- or worse, the top layer of skin starts falling off -- it allows bacteria to enter and fluid to leak out.
If you have a picture of your own burns or injuries, submit your injury pictures here.
Any opinions expressed here are for educational purposes only and are not intended for diagnosis.