We wanted to advise you how we responded to that inquiry:
“Yesterday, the blast furnace teams were still working to recover from the earlier bleeder pop conditions. During the recovery time, it is normal practice to use steam in the process which is then periodically vented from the top of the furnace. The venting can happen from time to time over the next few days until the furnace recovers back to normal production. The photos you shared display a period (around 18:36 on Oct. 3rd) when this venting was happening. As is typical with steam, it can also appear much darker (depending on the observer’s position) with certain angles of sunlight such as in the morning and evening.”