Which of the following is an important tool when inspecting heat duct systems?

A thermographic camera is an important tool when inspecting heat duct systems because it allows for the visualization of temperature differences in surfaces. This tool can identify areas where there may be heat loss or gain, indicating inefficiencies in the ductwork, insulation issues, or where air leaks may exist. By detecting these variations in temperature, inspectors can better assess the condition of the heating system, which is critical for ensuring optimal functionality and energy efficiency.

While moisture meters can detect dampness, they are more relevant for assessing potential moisture damage or issues, rather than evaluating the performance of heat duct systems. Sound level meters are useful for assessing noise levels, which might indicate operational problems but do not provide information regarding heat transfer efficiency. Smoke pens are beneficial for demonstrating air movement and can indicate leaks, yet they do not provide the detailed thermal information that a thermographic camera offers. Therefore, the thermographic camera stands out as the most effective tool for this specific purpose.