What is backdrafting in relation to combustion appliances?

Backdrafting occurs when combustion gases, rather than being properly vented outside, are drawn back into the living space. This is often caused by improper ventilation or changes in pressure within the home, such as exhaust fans or negative pressure created by other appliances.

The correct choice highlights continuous spillage with reversed chimney flow, which describes a situation where the flow of flue gases is not just a single event but becomes a repeated issue due to persistent negative pressure. When the chimney or vent is unable to exhaust gases correctly, and the flow is reversed, it increases the risk of exposure to harmful gases, including carbon monoxide.

This issue is crucial in ensuring the safety and proper functioning of combustion appliances. Recognizing and addressing conditions that lead to backdrafting is essential for maintaining air quality and preventing potential poisoning in residential spaces.