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COVID-19: HVAC Considerations for Re-Occupying Buildings

As the country begins to contemplate easing social distance restrictions, we have received many inquiries as to what facility operators should do to prepare their buildings for re-occupation. FEA recommends following these helpful guidelines to better prepare your building for safe and healthy occupancy.

Purge building 24-Hours before occupancy.

  • Place HVAC air handling systems in operation with outside air dampers opened as much as possible and no less than their designated minimum outside air position. If conditions outdoors permit air-side economizer operation, then allow system to operate in economizer mode. If weather is extreme and outside air cannot be increased above minimum in order to provide comfort conditioning, then leave outside air dampers at their scheduled minimum outside air position, no less.

  • Operate bathroom exhaust systems and other general exhaust system if provided in order to exchange stale indoor building air for outside air.

  • Disable Demand Controlled Ventilation (DCV) systems to keep outside air dampers from closing. This can be performed by reducing space or return air CO2 set-points to a very low setting (150 PPM for example). Since ambient outdoor air contains roughly 350 PPM CO2, the outside air will not be reduced with a setting of 150 PPM in systems with DCV control in place.

HVAC Air Handling Filters

  • Replace HVAC air handling system filters with clean, MERV 13 minimum air filters or highest efficiency compatible with system considering air pressure drop and filter rack size. Seal edges to reduce or eliminate bypass.

HVAC Operating Schedules

  • Once normal occupancy returns, consider extending hours of HVAC system operation to enhance dilution effect. This includes adjusting the set-back schedules and increasing building ventilation through more air-side economizer or less energy recovery.

Plumbing Fixtures

  • Ensure all plumbing traps are sealed

  • Prior to occupancy, top off all plumbing traps with water to restore trap seal that may have evaporated during the long unoccupied period. Fixtures with external plumbing traps include but are not limited to the following: floor drains, bathroom sinks and lavatories, shower stalls, mop sinks and janitor sinks.

  • While making these rounds, manually flush fixtures with integral traps such as water closets and urinals to restore the integral trap seal which also may have evaporated from these fixtures.

Domestic Water

  • Flush the domestic water system for approximately 30 minutes to purge out bacteria that may be forming in standing water inside pipes. This includes all faucets (hot and cold), drinking fountains, coffee makers, ice machine, etc.

Additional HVAC Considerations for the Long Term

  • Portable room air cleaners with HEPA filters.

  • UVGI (ultraviolet germicidal irradiation), for installation on air handling systems downstream of cooling coils. These must be properly designed and installed to prevent service personnel from radiation exposure.

Non-HVAC Related Preparation Before and During Occupancy

  • Increase disinfection of frequently touched surfaces.

  • Install more hand sanitation dispensers, assuming they can be procured.

  • Supervise or shut down food preparation and warming areas, including the office pantry and coffee station.

  • Close or post warning signs at water fountains in favor of bottle filling stations and sinks, or even better, encourage employees to bring their water from home.

  • Review human resource policies to make sure they are consistent with public health recommendations and all state and federal guidelines.

  • Identify a workplace coordinator who will be responsible for COVID-19 issues and their impact on the facility’s daily operations.

  • Encourage social distancing.

  • For additional information on preparing and cleaning your facility and best ways to address any potential COVID-19 issues, please consult the website.

Should you have any specific concerns or questions please don’t hesitate to contact us at, 860-677-2285 or on our website at


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