Which of the following appliances is classified as vented?

Furnaces are classified as vented appliances because they are designed to safely expel combustion gases, such as carbon monoxide and water vapor, produced during the combustion process. Vented appliances have a system that channels these gases to the outside of the building, typically through a flue or chimney. This is crucial for ensuring indoor air quality and preventing the accumulation of harmful gases inside the living space.

In contrast, gas ranges, indoor propane heaters, and stove tops may not always have dedicated venting systems. While some cooking appliances can be vented using range hoods, they often allow for the accumulation of combustion byproducts within the kitchen environment, especially if they are used without adequate ventilation. Therefore, furnaces stand out as the only option in the list that definitively requires and utilizes a venting system to operate safely.