Warm humid air, a cool chimney, soot or creosote deposits, moisture, and house pressure can combine to move fireplace odor into living space. Exhaust fans, clothes dryers, air handlers, and tight construction can influence airflow. Water or animal contamination can add different odors.
Chimney sweeping and cleaning may reduce odor sources when deposits are present, but cleaning alone will not correct a leak or pressure imbalance. Draft and smoke diagnosis evaluates airflow and system conditions. Water signs may require chimney leak repair, while wildlife evidence can call for animal and nest removal.
Avoid masking persistent odor with fragrance or sealing the fireplace without understanding venting and appliance requirements.