And if you use an auto darkening helmet and look out through the corner of the lens in a tight position you'll burn your eyes as well, as they don't darken on an angle, well at least the ones in Australia don't. I was welding frame in the corner of a shed and my eyes were burning, I worked out the cause and thought my cheaper helmet was the problem, went and had a look at a $350 helmet and put it up to the light, same thing, beware.
Got a flash late one night when I was a young fellow, went to the Ambulance station on the way to work the next morning and the guy behind the desk said " you've been welding" as I walked up!