The Noises Coming Out of Your Commercial HVAC System

Noises coming from an HVAC system are concerning, especially in a commercial environment where they’re large and complex. In Walnut Creek, CA, well-maintained HVAC systems in commercial buildings should run quietly and efficiently. A consistent, loud noise likely indicates malfunction or damage. Therefore, you should look out for these sounds:

Whistling or Hissing

Whistling in ductwork indicates loose connections or broken seals. A loose connection or broken seal causes air leakage and reduces airflow. Reduced airflow and air leakage cause low-pitched whistling or hissing.

Leaking refrigerant also sometimes produces a hissing or whistling sound. Hissing that sounds like a scream indicates dangerous pressure buildup in the compressor. If this occurs, shut the system down immediately.


In most cases, clicking is a normal component of HVAC operation. The system makes a clicking sound as cooled or heated air moves through contracting and expanding ductwork. However, clicking sometimes indicates malfunctioning, like a faulty sensor or igniter.


Booming in an HVAC system signals an emergency. Dirty burners restrict gas flow and cause toxic gas buildup. When burners ignite, this gas burns off or explodes, causing a booming sound.

Gas buildup and veritable explosions inside the heating unit are dangerous and hazardous to your building and employees. If you hear these types of sounds, evacuate immediately and call a professional to evaluate the safety of your indoor air.


A squealing or squeaking sound is normal in aging or heavily used commercial HVAC systems. The sound results from a broken belt in the heating unit or unlubricated parts.


Rattling in a HVAC system isn’t a major cause for concern. It’s usually caused by open access doors or loose exterior components.

Noises coming from commercial HVAC systems aren’t abnormal, but some sounds are more serious than others and indicate dangerous problems. If you’re unsure of what a noise means, call the experts at Contra Costa Climate Control for help.

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