A fireplace is more than just bricks and fire its inner structure is designed to channel smoke efficiently. Firebox: the combustion zone where heat is produced. Throat: a narrow passage that guides hot gases upward. Smoke chamber “lung”: expands and controls airflow, preventing smoke from backing up. Flue: the vertical shaft that vents smoke outside. Firebrick: retains heat and protects the inner walls. Proper ventilation and smart design prevent smoke from entering the home and boost heat efficiency. Knowing how warm air flows is key to building a safe, effective fireplace.