The smell or smoke coming down the chimney is a result of your house loosing too much air from the unsealed attic hatch.
Smoke in attic from chimney.
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.
If you have no smoke coming into your attic or other fireplace you ve confirmed.
This is the black smoke you see leaving a chimney when it s in use.
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.
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 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.
Shine a light up the flue to make sure there are no raccoons on the damper and smoke shelf.
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.
Now place another fan in a window on the opposite side of the home.
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.
If you ever had a chimney fire i wouldnt rely on the render stopping further damage.
Rerendering may stop the smoke but my advice would be to fit a twin wall stainless steel liner.
When you turn on both fans this will pull out the smoky air while you are drawing in new fresh air.
The warm air should rise out of your chimney including the smoke produced.
The reason is because when a chimney is being used and smoke is emitted it carries waste particles from the fire.
The best way to get rid of this smoke is by placing a box fan in the same room as the fireplace.
Start a small test fire and this time open a window in the same room as the fireplace with the restored chimney.
A warm air siphon must be created before a fire can burn properly and draw correctly.