If Vic is not hurt, then you don't need the first aid kit.
The furnace itself is right of the table with chainsaw on the workbench - close to the windows.
Go to what is shown in the picture below, it is opposite side of the workbench.

Then Click on the control box on the wall between the windows right of the furnace. See the cursor on the picture above - that's where the control box is located.
Then turn around andd go to the opposite wall and see the windows and the still. See picture below.

Press the control box there to open the windows on that side.