Fireplace smells and chimney flue odours may be attributed to a multitude of different things. Sometimes known as 'campfire like smells' most fireplace smells come from creosote deposits in your chimney. These odours can be worse in summer when the humidity is high, when your air conditioner is running or when it has been raining.
Sometimes once the flue is clear of creosote, the smell still exists and is usually due to pressure problems. As air travels down the chimney it brings the inner fireplace smells and chimney odours along it straight into your home.
If you are experiencing these odours it is best to contact a professional chimney ssweep in your area. They can assess your chimney, pin point the cause and prescribe a solution. A good understanding of airflow patterns and fireplace construction is essential for this job so make sure you contact a professional chimney sweep with extensive knowledge.