What is the hazard of a negative draft condition in a gas-fired appliance?

• A. Backdrafting and CO exposure into the living space.
• B. It reduces sound
• C. It improves energy efficiency
• D. It enhances ventilation

Answer: (A)

Negative draft means the vent system isn’t drawing combustion gases up and out as it should. When the draft is negative, those gases can be pulled back into the living space instead of exiting outside, a situation called backdrafting. Since gas-fired appliances produce carbon monoxide during combustion, this backflow can lead to CO exposure for occupants. Wind direction, a blocked flue, a closed damper, or other pressure differences in the home can create or worsen negative draft, making backdrafting more likely. That’s why the main hazard here is backdrafting and carbon monoxide entering the indoors.