Which of the following is an exception to the requirement for fuel-burning equipment to be connected to a chimney or vent?

Fuel-burning equipment typically must be connected to a chimney or vent to ensure that harmful gases, such as carbon monoxide, are safely expelled from the living space. However, there are specific exceptions to this requirement.

When equipment is labeled for unvented operation, it means that the manufacturer has designed the equipment to function safely without the need for venting. This labeling indicates that the appliance has been tested and meets safety standards for indoor use without a chimney or vent. These appliances usually incorporate specific safety features, such as oxygen depletion sensors or catalytic converters, to minimize the risk of harmful emissions.

In contrast, simply being old or portable does not exempt fuel-burning equipment from venting requirements; these characteristics do not ensure its safety without proper ventilation. Additionally, appliances that do not use fuel do not fall under the purview of fuel-burning equipment and thus, the venting requirement is not applicable at all. Therefore, the distinction of being labeled for unvented operation is critical and makes it the correct answer.