When you turn on both fans this will pull out the smoky air while you are drawing in new fresh air.
Smoke in attic from chimney.
The warm air should rise out of your chimney including the smoke produced.
If you have no smoke coming into your attic or other fireplace you ve confirmed.
A warm air siphon must be created before a fire can burn properly and draw correctly.
As soon as the raccoons are gone call a certified chimney sweep to clean your chimney of all nesting debris and install a chimney cap.
The smell or smoke coming down the chimney is a result of your house loosing too much air from the unsealed attic hatch.
Start a small test fire and this time open a window in the same room as the fireplace with the restored chimney.
The best way to get rid of this smoke is by placing a box fan in the same room as the fireplace.
Rerendering may stop the smoke but my advice would be to fit a twin wall stainless steel liner.
These waste particles build up and can get accumulated on the interior walls of the chimney and especially in any cracks there may be in the masonry.
Shine a light up the flue to make sure there are no raccoons on the damper and smoke shelf.
There is tremendous heat from chimney fires i have seen stacks split from the heat so for peace of mind get a liner in preferably by a hetas registered installer.
If you ever had a chimney fire i wouldnt rely on the render stopping further damage.
This is the black smoke you see leaving a chimney when it s in use.
The reason is because when a chimney is being used and smoke is emitted it carries waste particles from the fire.
If your flue system is not warm when lighting the fire then you can alter the ability of the fireplace to draw properly creating potentially harmful smoking problems.
Sometimes it is simply the conditions of the day or the way draughts move around a particular house or the wind being in a particular direction.
That air has to be replenished because your house is not going to implode and so it is going to reenter the house whichever way it can.
Now place another fan in a window on the opposite side of the home.