Which of the following is a common issue when air velocity is too high in a duct?

When air velocity is too high in a duct, one common issue observed is noise generation. High air velocity can lead to turbulence and friction within the ductwork, resulting in unacceptable noise levels. The sound produced is often due to the air rapidly moving through the narrow confines of the duct system, which can cause vibrations and resonance in the duct materials. This noise can be disruptive and is often a sign that the system is not operating optimally.

The consequences of increased air velocity often extend beyond noise. For example, while higher velocities can sometimes contribute to increased temperature due to friction, this is not as widely recognized as a primary cause compared to the noise factor. Likewise, the efficiency of the system can be affected by high velocity, but the immediate and noticeable impact is often the sound created. Inadequate airflow can also arise from several factors, but it typically relates more to poor duct design or blockages rather than high velocities directly.

Thus, the primary concern associated with excessively high air velocity in duct systems is indeed the generation of noise.