Which component is essential for safely venting combustion gases from appliances?

The correct choice, which is the chimney, plays a crucial role in safely venting combustion gases generated by appliances. A chimney is specifically designed to carry toxic gases such as carbon monoxide and other byproducts of combustion out of a building.

By creating a draft through the height of the structure, a chimney ensures that the gases rise and exit at a safe distance from the building and any areas where people gather. This helps to prevent the accumulation of harmful gases indoors, which can pose serious health risks. Additionally, the chimney's construction must meet specific building codes and standards to ensure its effectiveness and safety.

While other components like exhaust fans, draft hoods, and ventilation ducts also contribute to the overall ventilation of an appliance system, they do not fulfill the primary purpose of safely expelling combustion gases from the appliance to the outdoors as effectively as a chimney does. An exhaust fan is generally used to facilitate airflow but does not provide the vertical rise necessary for proper venting. A draft hood aids in regulating the draft but is not an outlet itself. Ventilation ducts assist in conducting air but are not exclusively used for venting combustion gases outside, making the chimney the key component in this context.