Ventilation

COVID-19 is thought to spread mainly from person-to-person through respiratory droplets. Changes to building operations, including the operation of Heating, Ventilation and Air Conditioning (HVAC) systems, can reduce airborne exposures. It is therefore critical that ventilation within a venue is carefully considered as a means of helping to prevent the spread of COVID-19. Portable fans are not recommended as they can further spread droplets and aerosols.

It may be challenging for Venue Manager to improve HVAC operations. These challenges may include:

  • Venue Manager is a tenant in their venue and therefore has limited or no control over maintenance, performance or improvements to HVAC systems
  • HVAC systems within the venue may not be capable of adjustments to recommended settings in a COVID-19 environment
  • Changes or improvements to HVAC systems can be very expensive and increase operating costs
  • Venue Manager may not have in-house expertise in the operation of the venue’s HVAC system

Although labour and financial resources may prevent changes or improvements to HVAC systems, Venue Managers must still make efforts to improve ventilation with the available resources.

HVAC systems may be maintained in-house, through an external contractor or by the venue owner (when the venue is not owned by the Venue Manager). The following points can offer a starting point for discussions when looking to increase HVAC effectiveness.

Fresh Air

Ventilation is the intentional introduction of fresh air into a space while the stale air is removed. This maintains the quality of air in a space, and can help limit the transmission of COVID-19. However, outside air temperatures in Toronto can make a supply of 100% fresh air challenging depending on the season. As well, large volumes of fresh air can increase wear on HVAC systems and substantially increase operating costs. Where possible, venues should increase ventilation rates through natural or mechanical means, preferably limiting the recirculation of air where possible. The following items can be considered:

  • The ACH, or air changes per hour in simplified terms, is the number of times per hour that the air in any given room is replaced with mechanical and/or natural ventilation. HVAC specialists should be consulted to determine the best ACU for any occupied space, and HVAC operations should be adjusted to match the recommended ACH (8-15 ACH for auditoriums). Where possible, the ACU should be adjusted upwards when considering COVID-19
  • Either before or after patrons enter or exit a venue, flush the auditorium for a sufficient duration to reduce the concentration of airborne infectious particles by 95%. For a well-mixed space, this would require three air changes of outside air. Where resources do not exist to determine this, flush the auditorium with as much fresh air as possible for three hours. This same approach can be applied for offices, rehearsal halls, shops, etc., at the start or end of a day
  • Increase the percentage of outdoor air by using economizer modes of HVAC operations potentially as high as 100%. Before increasing outdoor air percentage, verify compatibility with HVAC system capabilities for both temperature and humidity control, as well as compatibility with outdoor/indoor air quality considerations
  • Where the ability to increase fresh air through mechanical means does not exist, consider using natural ventilation such as opening windows if it is possible and safe to do so
  • Research indicates maintaining space relative humidity between 40‐60% decreases virus infectivity

Filters

  • Minimum Efficiency Reporting Value (MERV), is a system used to evaluate the efficiency of an air filter based on how effective it is at catching particles of varying sizes. The higher the MERV rating, the higher the air filtration capabilities of a particular filter
  • A minimum filter efficiency of MERV 13 is recommended to reduce transmission of COVID-19. This can be done as a special project or at the next required filter change. Where system design allows, filters can be changed to the highest efficiency filter a system can handle. A cost/benefit analysis should also be considered for the slight benefit of using the MERV 15/16 filters instead of the MERV 13. MERV 6-8 pre-filters are also recommended, where possible
  • Filters should be replaced as recommended by the manufacturer or HVAC specialists but increased filter changes are not required.
  • Ensure filter housing and racks have appropriate filter fit and check for ways to minimize filter bypass

HVAC Upgrades
Where resources allow, venues may consider upgrades to existing HVAC systems. These upgrades could include:

  • Changes to systems that allow for the use of higher-efficiency filters (minimum MERV 13)
  • Installation of UV-C lamps into ductwork. UV-C light inactivates viral, bacterial and fungal organisms so that they are unable to replicate and potentially cause disease

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