Preparing your HVAC for Re-Opening

HVAC Preparation Steps to take when re-occupying a building

Consequences of the COVID-19 pandemic with respect to commercial building occupancy levels impacted most places by March 15th, 2020. Government Policies stipulated business operations closures and restrictions as a means of achieving social distancing. Businesses also implemented additional measures on their own accord.

As most occupants transitioned to work-from-home arrangements, building technical systems experienced a decline in their operational requirement. Additionally, these workspace changes have occurred during a seasonal climatic “shoulder period”. The combination of reduced equipment loads as a result of low occupancy levels, combined with moderating outdoor temperatures suggests that many technical systems have seen little use. Specifically, for the cooling systems, it is likely that many have not received their Spring/Summer start-up routines. 

Other facility infrastructure systems such as those listed below will also have been subject to low usage levels. 

Operational resiliency and health and safety shall be paramount as you prepare your facility for re-entry. Each building owner, manager, operations team and their various technical service providers should discuss and agree what activities constitute the most appropriate facility re-start procedure. Facility use, design, age, types of systems, any known issues, and level of ongoing maintenance since March 1st, 2020 will be key considerations.  

The teams at GDI Integrated Facility Services and Ainsworth urge each owner or manager to collaborate with their resources to implement a simple re-start plan for each technical area. The physical condition and operation of equipment and services supporting the building should be assessed. We suggest that each of your technical infrastructure service providers conduct what is considered their more robust level of preventative and predictive maintenance routines as preparation for re-entry. All tasks do not necessarily contribute specifically to COVID-19 mitigation measures but should provide the peace of mind and confidence that your key systems are able to respond and perform at a high level. 

  • Mechanical Systems  
    • Chilled/condenser water: open/closed loops (cooling towers) 
    • All Ventilation and (booster) pumping systems 
    • Discuss staged cleaning of ventilation ductwork 
    • Evaporators and evaporators pans 
    • Discuss cleaning and sanitization of supply and return grills  
  • Building Automation 
  • Electrical Systems 
  • Water, Sanitary Systems, Traps, Sumps 
  • Water features  
  • Elevating Devices  
  • Potable water: flush faucets  
  • Fire Life Safety Systems  

Fan Section 

  1. Check Filters; change and date if not acceptable 
  2. Clean and sanitize evaporator coil & drain pan 
  3. Check if fans have turned on and air is moving in and out of building 
  4. Inspect motor, pulleys, belts, blower wheel and bearings 
  5. Inspect dampers (outside and return), which help control fresh air to the building 
  6. Check overall building pressure and critical spaces to make sure they are positive 


  1. Inspect wiring, operational and safety controls, disconnects and fuses
  2. Inspect and set thermostat or EMS
  3. Check that the devices and sensors are within an acceptable calibration for controlling space comfort and ventilation 
  4. Check if alarms and alerts are set up and their communication path is correct i.e. it is notifying the right person. 


  1. Verify cooling performance; check the delta’s and if out of range, check if the refrigerant is adequately changed 
  2. Inspect and clean condenser coil with an approved cleaning solution 
  3. Inspect economizer, compressor, condenser fan, and blade 
  4. Check coil leaving air temperatures to ensure the system is providing dehumidification 


  1. Inspect and clean burners/heat exchanger 
  2. Inspect hot gas bypass, ignition and safety controls 
  3. Inspect operational controls/valves 
  4. Verify fuel source is on and available 

Building systems should be started methodically to prevent load shed from a simultaneous start

Depending on length of time equipment has been inactive, systems should be allowed to run for a period with careful observation to ensure valves, switches, seals etc. are operating correctly 

Building employees responsible for assessing the physical structure and building systems must be licensed or certified for their activities and should refer to all authority having jurisdictions.     


Many commercial building owners, managers and operators continue to pose COVID-19 questions specifically related to their HVAC system. These questions centre on the concern that the HVAC system may contribute to spread of COVID-19. It is important that these concerns be addressed with information and facts from accredited sources such as ASHRAE, WHO, and CDC as examples.

In April 2020 it has been widely reported that HVAC systems may contribute to the spread of the disease. We would like to address one of such recent reports involving a restaurant in China that has drawn much international attention.

According to WHO, there is no evidence suggested contaminated droplets are circulating in the ventilation system. As further studies are completed, GDI Integrated Facilities shall provide more information.

What is the HEPA filter and should I be using HEPA filter in my HVAC system? 

HEPA is a type of pleated mechanical air filter. It is an acronym for “high-efficiency particulate air”. This type of air filter can theoretically remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm). (1)

The SARS-CoV-2 virus that caused the global COVID-19 pandemic in 2020 has an average size of 0.06 microns to 0.15 micron in diameter. Accordingly, to current evidence by WHO (2), the SARS-CoV-2 virus is primarily transmitted through respiratory droplets at a size larger than 5-10 μm in diameter which is much larger than the naked virus itself.

Technically, if these larger size droplets that contain viruses do reach the return air stream HVAC filters, a significant portion can be captured depending on the MERV rating of your filter. As an owner/operator, if you are operating according to the minimum standard of ASHRAE Standard 52.2 of MERV 8, and will like to improve the filtration capability, we will recommend you to discuss it with your local contractor on the use of higher-grade filters, such as MERV-13. Please refer to the MERV Filter Rating chart on the following page.

There are several key considerations when using higher rating filters

  • The filter will trap the virus, but not kill it. So proper disposal of the contaminated filters is required to contain the further spread of the virus.
  • Your ventilation system may not be designed for the characteristic of higher rating filters. Make sure to check with your local HVAC contractor to confirm if you can still maintain the system’s design performance.

So how can the HVAC system contribute to the spread of SRAS-CoV-2 and other viruses?

Supply air is provided through air grills and diffusers that are located throughout the occupied space.  Depending on the diffuser design and the characteristics of the airflow, the velocity will vary.  A higher velocity of air movement can propel contaminated droplets a further distance resulting in these droplets staying in the air for a longer period.  Occupants who practice recommended social distancing may still be subject to droplet exposure under the above-mentioned circumstances.  An indication that this situation may exist in your facility is the periodic occupant complaints about drafty air. 

An incident report that reflects this condition is documented by the CDC and can be view via the link below for your reference.   This is one of the incidents that has been widely reported. 

It is recommended that you consider the following action items in identifying potential risk of higher than normal supply air velocity. 

  • Speaking with building occupants and maintenance personnel 
  • Discuss and review potential risk with your maintenance contractor 
  • Consult with your maintenance contractor on air balancing to ensure the system is operating as the original design 
  • Review of existing drawing and design with engineer and contractors 

MERV Filter Description List

Summary of Considerations