Step 2 of Restarting your HVAC

BY Burns Mechanical IN Maintenance, Service

Written By Dan Kerr, P.E. (President, Burns Mechanical, Inc.)


As the Philadelphia region prepares to re-open commercial facilities, significant questions arise regarding the capabilities of HVAC systems to reduce the risk of viral infection. Product claims and business opportunists abound in an environment of fear. It can be overwhelming.

We’ve spent a significant amount of time synthesizing the latest engineering and scientific evidence against the backdrop of what we’ve learned from decades of engineering, building, commissioning, and maintaining HVAC systems. Though no “one size fits all,” we’ve attempted to break a large problem into a 3-step process, focusing on un-biased fundamentals. Our first post in this series focused on the primary importance of introducing proper outside ventilation air into your building. This article focuses on a frequently overlooked but essential practice: continuous commissioning and maintenance.


STEP 2: Continuous Commissioning & Maintenance


To meet health and cleanliness standards, hospitals and pharmaceutical facilities have to satisfy on-going accreditation and validation requirements from regulating agencies. Subsequently, the most critical HVAC system operating requirements, such as confirmation of adequate ventilation and pressure gradients for infection control, are continuously maintained and validated.

Lacking such enforcement, only a select few of commercial facility operators take the time and effort to validate HVAC system performance to ensure proper environmental control. Poor results, like those of the school described in our previous post, are inevitable. We strongly recommend taking this time to develop a basic re-commissioning strategy as you prepare to re-admit occupants indoors. Take notes on what you learn from the process, and then commit to periodic checks to ensure long-term indoor environmental quality.

Using our own facility as an example, we trended temperature, relative humidity, and carbon dioxide over several days in those areas occupied by employees (inexpensive portable data recorders are available for this purpose if your Building Automation System lacks the capability). The attached chart illustrates a sampling of results and validates that our systems are still operating to the environmental criteria for which they were originally designed. While not a substitute for proper distancing, hygiene, and cleaning practices, the HVAC testing results offer an added measure of safety as we emerge from our shelter-in-place restriction.

Chart trends temperature and CO2 in an occupied office area

Our HVAC systems aren’t anything special – just your standard off-the-shelf tenant office variety. They are, however, well maintained and we have kept them operating as normal throughout the pandemic. To answer a common question, there is no evidence that virus is spread through commercial HVAC systems. You should keep them operating, most especially to allow the outside ventilation air to dilute any build-up of contaminants.

If you have chosen to shut down your commercial HVAC system over the past several weeks, or if you have deferred or otherwise question the quality of your HVAC maintenance, your start-up process should be more cautious. Those in this camp need to be concerned about moisture – both where it has migrated to and where it has been sitting stagnant.

Legionella can form in stagnant water systems, both HVAC and plumbing. If your system has been sitting stagnant through our stay at home order, you should be flushing and disinfecting prior to use. Mildew and mold are another risk, especially during the humid weather we’ve had through the spring and early summer. Mold grows in the presence of three elements: moisture, darkness, and food (dust, dirt, fabrics, etc.). Conduct a thorough inspection of any area of your facility where these three ingredients might have been present.

Our next post will concentrate on a topic of mass confusion – air cleaning and disinfecting devices. We’ll give you our take sometime next week!



*Helpful Independent Links:

ASHRAE Epidemic Task Force, Useful Resources

ASHRAE Position Document on Filtration and Air Cleaning

How can airborne transmission of COVID-19 indoors be minimized?