This fireplace has been boarded over, clearly not having been used for a considerable time.
Smoke staining on the surround over the fireplace suggests a problem. Peeling back the boarding you can see a fall of soot and various accumulated debris.
Ventilation is obviously restricted, posing a personal safety risk. The flue must be swept before use and preferably your contractor should conduct a smoke test to ensure it is providing proper ventilation.
It is unclear if the flue is lined. This will need to be checked and a liner installed if you intend to fit a gas fire or similar appliance.