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

In Progress


Work and Health

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.

Below please find the initial collaborators on this project. We will be building the team and the research approach and focus over the coming months.

Pat O’Campo is an international leader in Social Epidemiology and Tier 1 Canada Research Chair in Population Health Intervention Research. She is Executive Director of the Li Ka Shing Knowledge Institute at Unity Health Toronto, and Professor of Epidemiology at the Dalla Lana School of Public Health, University of Toronto.

LLana James is the AI, Medicine & Data Justice Post Doctoral Fellow at Queen’s University. Her work focuses on the ways that health care, public health and medicine amplify structures such as racial capitalism through practices that show up in people’s work, bodies and everyday lives.

Jeffrey Siegel is an air quality expert and a Professor in the Department of Civil and Mineral Engineering at the University of Toronto.

Linn Holness is an occupational medicine physician and a Professor Emerita at the Dalla Lana School of Public Health and Department of Medicine at the University of Toronto. She is a staff physician in the Division of Occupational Medicine in the Department of Medicine at St. Michael’s Hospital and a scientist at MAP. She is also the Director of the Centre for Research Expertise in Occupational Disease.

Amy Katz is a Knowledge Translation Specialist (KT) at MAP. She works with networks of people and organizations to intervene directly in institutional practices and narratives.


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


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

Contact Info

Amy Katz