I use a faceshield that fits onto a hardhat.
I have clear and tinted face shields.
I wear tinted glasses under the faceshield to protect from the IR radiation.
It is a good idea to wear some thin leather or something under the hardhat, and extending over the shirt/leather jacket collar, to protect the neck.
The plastic faceshields will melt easily if you lean over a bit to look into the lid opening.
I use a refrigerator shelf in front of the face shield when I have to look into the furnace.
I also have a metal mesh face shield, and it works well, but does not fit onto a hardhat.