Rapid review: Does Toronto Public Health emphasize indoor air quality in its public COVID-19 advice to congregate settings?

In Progress


Work and Health

What we did: In May, 2021 Toronto Public Health (TPH) published a Congregate Living Settings Toolkit which, “…provides an overview of resources for those working on COVID-19 prevention and response in congregate living settings (e.g., shelters, group homes, supportive housing).” We looked in detail at resources listed in the toolkit, and focused on what they had to say about indoor air quality.

Why we did it: Since 2020, scientists, engineers and physicians have been sharing evidence demonstrating that COVID-19 transmission is airborne, and urging public health authorities in Ontario and around the world to take a action. Improvements to indoor air quality are central to addressing airborne transmission. These improvements can be accomplished through ventilation, filtration and, in some cases, ultraviolet disinfection. Find out more about how community spaces can improve indoor air quality here.

Congregate settings are high-risk sites for COVID-19 infection. While vaccination has reduced this risk, breakthrough infections and evolving variants require ongoing measures for COVID-19 infection prevention and control. We wanted to explore TPH’s approach to indoor air quality in the spring of 2021, more than one year into the pandemic. In particular, we wanted to know if TPH was emphasizing indoor air quality in its public advice to congregate settings about COVID-19.

What we found: In the spring of 2021, TPH was not emphasizing indoor air quality in its public COVID-19 advice to congregate settings. The resources listed in TPH’s “Congregate Settings Toolkit” provide almost no guidance related to ventilation, HVAC systems, portable air filtration or ultraviolet disinfection. As result, some congregate settings in Toronto such as shelters may not have the information or supports they need to implement evidence-based practices to help reduce airborne transmission of COVID-19.

Read the full report and detailed methods.

Context for TPH guidance: Most of the materials cited in TPH’s toolkit are sourced from Public Health Ontario, and most of these contain no references to airborne transmission of COVID-19 outside of the context of aerosol-generating medical procedures. Several other Public Health Units in Ontario also seem to be following the province’s lead, relying heavily on Public Health Ontario and Ministry of Health materials in their public guidance for congregate settings.

Urgent recommendations for public health: In 2007, the SARS commission’s final report found that denial of airborne transmission may have been a factor in generating preventable death in Ontario. The report urges decision-makers to adopt the precautionary principle in the context of public health pandemic measures, and makes explicit mention of the failure to adopt this principle in the context of potential airborne transmission of SARS. Future inquiries may wish to explore the decisions, accountabilities and conditions in the Ministry of Health and Long-Term Care, at PHO and in Ontario’s public health units that led to similar dynamics during the COVID-19 pandemic.

As the pandemic continues, PHO and TPH should urgently and publicly:

  1. Build capacity and retain permanent expertise related to indoor air quality.
  2. Include metrics related to indoor air quality in all facility appraisals and inspections.
  3. Inform congregate settings in Toronto and province-wide that improvements to indoor air quality are key infection prevention and control measures for COVID-19 and other respiratory illnesses.
  4. Update all guidance to reflect the above and place caveats on outdated guidance.
  5. Ensure that individual guidance documents are clear, accessible and comprehensive—our review revealed a maze of lists, hyperlinks and web pages, many of which led to outdated resources.
  6. Ensure that all congregate settings receive and implement updated guidance. This includes providing practical supports to congregate settings to address indoor air quality and establishing evidence-based occupancy levels on an emergency basis.
  7. Ensure that guidance aimed at congregate settings in Ontario, including IPAC trainings, emphasizes the importance of engineering controls, and builds capacity to implement these controls. At present, public COVID-19 guidance for congregate settings in Ontario largely places responsibility for infection prevention and control onto individual workers instead of onto facilities and systems. For example, while resources for congregate settings rarely mention building-related measures such as HVAC improvements and ultraviolet disinfection, they provide detailed advice on cleaning and disinfection, handwashing, distancing signage and PPE (excluding N95 masks, which PHO guidance as of spring 2021 indicates should be reserved for aerosol-generating procedures).

About the Project: Examining the approach of public health authorities to ventilation and filtration during the COVID-19 pandemic in Toronto

In April 2021, leading medical journals including the Lancet, the Journal of the American Medical Association and BMJ published pieces from prominent scientists across disciplines asserting the importance of practices such as ventilation and filtration in reducing the transmission of COVID-19.1,2,3 Ventilation and filtration are part of a suite of preventive measures with the capacity to reduce transmission of COVID-19, often referred to as “infection prevention and control” (IPAC) measures.

In Ontario, IPAC measures for workplaces (including health care workplaces), congregate settings and multi-residential buildings are informed by Public Health Ontario (PHO), and mandated and enforced by local public health units such as Toronto Public Health (TPH).4 Provincial ministries such as the Ministry of Health and Long-term Care, the Ministry of Labour and the Ministry of Education also have a role in informing, mandating and enforcing safety within and in some cases across their respective sectors. Finally, various City departments participate in enforcing by-laws related to health and safety.

This project explores the approach of public health authorities to ventilation and filtration during the COVID-19 pandemic, with a focus on Toronto. We are particularly interested in how public health authorities respond to accumulating evidence related to airborne transmission. In the first stage of this work, we will conduct a document review of publicly-released materials from PHO and TPH. We will begin by exploring the way these public health authorities frame ventilation and filtration in the context of IPAC measures aimed at workplaces such as shelters, health care organizations and community services. We will explore current guidance and changes in guidance over time.

The first stage of the project will focus on Toronto as it is a Public Health Unit with a high burden of COVID-19 and a large number of health care workplaces, multi-residential buildings, community services and congregate settings, including, importantly, shelters and shelter hotels. If capacity allows, subsequent stages will include additional PHUs in the Greater Toronto Area.

In the context of other pandemics such as SARS, IPAC practices were examined after the fact through inquiries and research.5 Our goal is to examine the recommendations and practices of public health authorities while mitigation is still possible, and as evidence related to different modes of transmission accumulates. By feeding back this information to public health authorities, health care organizations, workplaces and the public during the pandemic, we hope to positively impact IPAC measures in real time.

We are particularly interested in this subject given the potential to rapidly mitigate airborne transmission of COVID-19 in workplaces. This includes immediate measures such as portable filtration, simple ventilation improvements, improvements to mask fit and filtration, a focus on outdoor activities where possible (e.g. meetings and vaccine clinics held outside), and safer occupancy levels. It also includes longer-term projects such as HVAC overhauls. For examples of these mitigation measures, please see this backgrounder.


1. Greenhalgh T et al. Ten scientific reasons in support of airborne transmission of SARS-CoV-2. April 15, 2021.

2. Allan AG & Ibrahim AM. Indoor Air Changes and Potential Implications for SARS-CoV-2 Transmission. April 16, 2021.

3. Tang JW, Marr LC, Li Y & Dancer SJ. Covid-19 has redefined airborne transmission. April 14, 2021. BMJ 2021;373:n913.

4. Augustin A, Richard C. COVID-19: Infection Prevention and Control (IPAC) for Regulated Health Professionals. June 22, 2020. (Webinar).

5. Campbell A. The SARS commission. December, 2006.


Work and Health


  • LLana James (Queen’s University)
  • Amy Katz (MAP)
  • Amy (Tianyuan) Li (University of Toronto)
  • Dr. Jeffrey Siegel (University of Toronto)

Contact Info

Amy Katz