There is currently a pretty big bug with the furnaces, both types. If they are on during a rain storm and the player is within visual range of them the lighting effects will make the screen flicker white really intensely. I am not prone to Epilepsy, however the flickering hurts so bad i had to quit playing the game. This really needs to be fixed before someone with epilepsy encounters this bug!!!
If someone wants to replicate this bug just go near “New Asagath” build a bunch of furnaces and wait till it rains. Once it does keep looking at the them, the flickering will start. The closer you are the faster they get.