Ventilation in the context of COVID-19

Current as of October 19, 2021

This page provides information about ventilation at McGill in the context of COVID-19.

On this page: Ventilation in your building | A/C units, fans, and air purifiers | Optimization of ventilation

Find out about ventilation in your building

McGill has many different types of buildings in use, from recently built structures to historic mansions. Some buildings are mechanically ventilated; others rely on natural ventilation.

1. Search this page to see if your building is mechanically ventilated or not.

2. Follow the recommendations below:

a) For mechanically ventilated buildings, no action on the part of the occupant is needed.
Discover what has been done to optimize mechanical ventilation and see the guidelines re air conditioning units and fans.

b) Buildings that are not mechanically ventilated will have a mix of spaces: those with windows that open and those with no windows or windows that do not open.

If your space has windows that open:

  • Open them to bring in fresh air when the room is unoccupied (for 10 to 15 minutes at least twice a day) but close your door when windows are open.
  • Follow the guidelines for air conditioning units and fans.
  • Do not leave the windows open overnight as this may result in frozen and burst pipes and water damage.

If your space does not have windows or they do not open:

  • Limit use of space to one user, unless authorized otherwise by FMAS
  • If the space needs to be used by more than one occupant, write to emergency.mgmt [at] to have FMAS conduct an assessment of the space before it is used.

Using air conditioning units, fans, and air purifiers:

The Institut national de santé publique du Québec has released guidelines for the use of air conditioning units (window or wall), electric fans, and mobile air purification devices in the context of COVID-19. These guidelines are for healthcare settings and for school settings and camps; however, some guidelines are adaptable to the university setting.

Air conditioners and fans

In general, air from a wall or window air conditioning (a/c) unit or fan should not blow directly on people .

  • The air flow caused by fans or a/c units should not be directed towards the exit door of the room or the unit to avoid the dispersion of droplets or aerosols out of the room or the unit.
  • The air flow caused by these devices should not be directed towards the occupants.
  • When two or more people share a room, operate fans or a/c units at low speed and do not direct the airflow towards the faces of the occupants or from one person to another.
  • If one person occupies a room with a fan or a/c unit, close the door if possible or ensure the air flow is directed away from the door.

Note that the guidelines for air conditioning units and fans do not apply to air vents connected to mechanical ventilation systems.

Mobile air purifiers

Mobile air purification devices (or air cleaners) are not advised in the classroom or workplace.

  • They are unproven in controlling transmission of aerosolized diseases and can potentially spread infectious aerosols if installed improperly.

"The group of experts does not recommend the use of mobile filtration devices(or air purifiers) in schools due to: 

  • Their unproven effectiveness at countering the transmission of diseases by aerosols (tuberculosis or other); 
  • Their reduced efficiency in a large room (such as a classroom) where sources of potentially infectious particulate matter are diffuse or remote; 
  • The risk of inappropriate use (possible generation of air flow carrying potentially infectious aerosols); 
  • The production of noise that  could interfere with concentration. 

Optimization of mechanical ventilation

McGill has implemented a number of measures to align with guidance from public health agencies and industry regarding the operation of heating, ventilation and air-conditioning (HVAC) systems, including from:

On July 19, Quebec’s Ministry of Higher Education strongly recommended that universities implement six measures to optimize ventilation for the Fall 2021 term, based on the Government report on Ventilation and Transmission of COVID-19 in the School and Health-Care Environments.

McGill is measuring CO2 levels in rooms without CO2 monitors to ensure air quality and proper ventilation. Please visit our CO2 Measurement Schedule and CO2 Measurement Results pages for more details. If anyone at McGill feels like the ventilation system is not working correctly (e.g. too hot/cold, little air movement) they are asked to call FCC at 4555.

Government Recommendations

McGill Measures Taken

  1. Ensure optimal maintenance and operations of ventilation systems, including filtration integrated in the systems.



All mechanical ventilation systems at McGill are equipped with air filters:

  • MERV-13 pre-filters provide an initial filtration that remove large particles and are replaced at least once a year.
  • Air filters are replaced once a year
  1. Optimize outside air based on the capacity of the HVAC system


All HVAC systems at McGill that recirculate air have been optimized to draw in the maximum of outside air.

  1. Avoid maintaining energy conservations strategies (e.g. on demand ventilation initiated and or regulated by a timer) to favour continuous ventilation of spaces


All HVAC systems have been set to run 24/7

  1. Maintain a minimum level of ventilation continuously, even when the space is unoccupied


All HVAC systems have been set to run 24/7

  1. Ensure required air exchanges per hour are met as stated in la “Loi sur la santé et la sécurité au travail”


All HVAC systems have been modified to operate with the maximum number of air changes per hour and meet at least the minimum standard of the law. All HVAC systems have been designed to follow the standards of the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE).

  1. Avoid the use of rooms for groups of people where ventilation is deficient or absent


McGill recommends single-person occupancy for rooms where ventilation is deficient or absent and without windows or with windows that do not open.

If this is not possible, contact emergency.mgmt [at] to arrange a ventilation assessment of your naturally ventilated space with no windows or windows that do not open. Requests should only be made by supervisors.



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