Which issue could result from improper ventilation in a gas furnace?

Improper ventilation in a gas furnace can lead to an increased risk of carbon monoxide poisoning, which is a significant safety concern. Gas furnaces rely on proper airflow to exhaust combustion gases, including carbon monoxide, safely outside the home. When ventilation is inadequate, these harmful gases can accumulate indoors, posing serious health risks to occupants.

Carbon monoxide is a colorless, odorless gas that can be extremely dangerous, as it binds to hemoglobin in the blood, preventing oxygen transport and leading to symptoms such as headaches, dizziness, and even unconsciousness or death in severe cases. Therefore, ensuring that a gas furnace is properly ventilated is crucial for maintaining indoor air quality and safety.

The other options present benefits that are not associated with improper ventilation. Improved energy efficiency, reduced noise levels, and enhanced heating performance typically require well-designed ventilation systems and are not outcomes of improper ventilation.