Which of the following factors affects chimney draft?

The factor that affects chimney draft includes outdoor temperature and wind conditions because these elements directly influence how air moves within the chimney.

When outdoor temperatures decrease, the difference between the temperature of the flue gases and the outside air increases, enhancing the draft; warmer air rises more effectively than cooler air. In addition, wind conditions can create pressure differences around the chimney, which either promotes or hinders the upward flow of air and combustion gases. For example, a strong wind blowing across the top of the chimney can increase the draft, while downdrafts caused by turbulent wind patterns can reduce it.

In contrast, while rain and humidity contribute to the overall environment, their direct impact on the draft is generally less than that of temperature and wind. The type of fuel burned can affect combustion efficiency but does not inherently govern the draft itself; it's more about how fuel affects the temperature of flue gases. Chimney height plays a role in draft creation through elevation, but it's just one factor; it must interact with both temperature and wind conditions to produce an effective draft. Thus, outdoor temperature and wind conditions are crucial for understanding and managing chimney draft effectively.