According to BPI Technical Standards, what should a smoke pencil be used to test?

A smoke pencil is specifically designed to visualize airflow patterns and help assess ventilation systems, making it particularly effective when testing airflow through an exhaust fan. When the smoke is introduced at the fan's intake or near the exhaust, it allows the technician to observe how the air is moving. This can reveal inefficiencies or issues with the ventilation system, such as leaks or unbalanced airflow, which are critical to understanding and improving indoor air quality in multifamily buildings.

The other options do not relate to the intended use of a smoke pencil. Humidity levels require hygrometers or moisture meters for accurate measurement. Temperature variations are best assessed with thermometers or thermal imaging devices. Identifying gas leaks generally involves the use of specialized gas detectors, which can safely identify the presence of specific gases rather than relying on visual cues like a smoke pencil provides.