Architects, Air and SarsCov2


Architects, Air and SarsCov2

We are approaching nearly a year of life with COVID-19, yet the pandemic appears to be only worsening. By the time this gets published, worldwide deaths will have exceeded 2 million, yet few countries seem to have this under control. The purpose of this post is to appeal to Ontario Architects and Engineers to consider how architectural and engineering interventions can reduce the transmission of this virus, just as it has with previous pandemics, most notably through improved ventilation, airflow design, pedestrian traffic and volumetric design. First of all we must accept that governments worldwide are failing to control COVID-19 due to a number of issues, but thousands of experts in epidemiology, medicine, engineering and infection control have been urging the WHO, CDC and governments to reconsider their stance on of airborne transmission, which can be explained as a problem of terminology, flawed science, historic assumptions and professional silos. A number of recent articles including this first numbered resource featured below from the Journal of Hospital Infection, unpacks the issues and provides clear guidance as we move through a second year of lockdowns and restrictions on social human activities. 

Part of the conclusion of the first article reads thus;

What does (…treating SarsCov2 as airborne…) mean for infection control practitioners in healthcare, as well as the general population? Aside from the obvious benefits of Personal Protective Equipment (PPE), the existing evidence is sufficiently strong to warrant engineering controls targeting airborne transmission as part of an overall strategy to limit the infection risk indoors. These would include sufficient and effective ventilation, possibly enhanced by particle filtration and air disinfection; and the avoidance of systems that recirculate or mix air. Opening windows, subject to thermal comfort and security, provides more than a gesture towards reducing the risk of infection from lingering viral particles.71,72,74 Measures to control overcrowding in both healthcare and confined indoor environments in the community, including public transport, are also relevant. There exist a range of cost-effective measures aimed at diluting infectious airborne particles in homes and hospitals that are easily implemented, without major renovation or expenditure.71,73 These will serve to protect all of us as we seek the evidence required to further reduce the risk from Covid-19 over the coming months and years. It is time to discard the myths and rewrite the science of viral transmission.


Architects and Engineers can and should take a leading role since our self-regulating professions are committed to serving the public interest, and when we are made aware of how the spaces we design can influence the transmission of Sars Cov 2, we are obliged to act on the information, providing both leadership and solutions. As a current VP (Strategic) of the Ontario Association of Architects, I am urging the OAA Council and its membership take a leading role in advising our Provincial government on the issues at the intersection of LTC and Healthcare Architecture, but also Schools, MURBs and Residences, and subsequently by providing our own membership, and allied professionals with the tools needed to assess and mitigate transmission of Sars Cov 2 through improvements to the built environment in terms of Indoor Air Quality measures and controls. The Ontario Society of Professional Engineers has taken just this kind of leadership with their recent public statement:

This blog post is a first step towards these goals.

While we could get right into the weeds with science and guidance, I would first point the reader to four critically important resources: 

  1. Covid Myths, Busted:
  2. An open letter that this author has co-signed with 362 other professionals in the fields of healthcare, research, engineering and infection control, about why our governments need to take airborne transmission of SarsCov2 seriously:
  3. This excellent summary of the science at this public document co-authored by numerous experts in the field here:
  4. Numerous HVAC and engineers have been posting webinars and forums on best practices in healthcare and ICI buildings, such as ASHRAE, which has even resulted in Public Health Canada recently (january 11, 20201) publishing this guide on Ventilation titled COVID-19: Guidance on indoor ventilation during the pandemic.

It should be noted that none of these recommendations negate or supercede any other public health directives or measures, but rather enhance these with ventilation considerations that for the most part, have been downplayed by the WHO and numerous public health agencies for reasons elucidated in the first resource linked above. SarsCov2 Transmission risks can be mapped on a matrix of measures, with increasing/decreasing risk according to the measures taken, as per the attached:


As Jonathan Mesiano-Crookston notes in his Twitter feed:

Jonathan expands further on the history below (copied with permission):

Before 1850, miasma theory said disease came out of swamps and killed you. Nobody really knew how.  We knew microorganisms existed, of course, since Robert Hooke’s description of molds in 1665 and Antoni van Leeuwenhoek of bacteria in 1676. However, in the 1800s people still thought microorganisms spontaneously generated in the environment (typically swamps and sewers) from vital force – an idea that dated back to Aristotle – and would infect at a distance. This was “miasma theory”.  It would be dead by the late 1880s.

In 1847, Semmelweis showed that childbed fever rates in obstetrics wards cold be slashed if doctors washed and disinfected their hands – they were carrying he contagion from person to person!

In around 1850, Dr. John Snow, a rather bright anesthesiologist who had worked with cholera patients, got the idea from his patients that cholera might be a pathogen that infects the gastrointestinal tract because of the symptoms he saw in his patients. His investigations led to the understanding that cholera was a pathogen transmitted in the water.  His famous investigation leading to the removal of the water pump handle at Broad Street was 1855. 

In around 1850, Edward Jenner could prevent smallpox, by infecting the host with scrapings of cowpox pustules.  However, nobody could explain why it worked: no microscope of the day was good enough to see the smallpox or cowpox virus!

In 1861, Louis Pasteur, who had investigated yeast for a client and observed bacteria growing in it, proposed germ theory, that suggested that all disease was caused by microorganisms. Koch took up this investigation, and he would prove this true in the late 1800s when he observed anthrax in the blood of infected cows.

After 1861, the 1800s turned into a sort of “race” to discover what microorganism caused what disease, and how it spread.  The causes of many diseases were discovered.  Also, how they transmitted.  Malaria was found to transmit not wafting through the air but by mosquito bites, for example, thus solving that mystery.

By the late 1880s, Louis Pasteur hammered the final the nail in the coffin of miasma theory by showing that that bacteria could not grow in a sealed container that had been sterilized. 

Shortly afterwards he developed the first vaccines as well, to anthrax, by weakening it with oxygen, chicken cholera, and later to rabies. This last led to the establishment of the Pasteur Institute. 

By 1900, it was reasonably firmly entrenched that micro-organisms caused illness, and that they did not arise spontaneously in the environment. However, where did they live?  It was still felt by some that they somehow grew in swamps and sewers and floated through the air.

In 1910, a public health officer from Rhode Island, Dr. Chapin, wrote his seminal Modes and Sources of Infection. It postulated that, for human diseases, rather than micro-organisms arising in swamps and sewers and infecting us over long distances through the air, micro-organisms (at least for many of the fevers and respiratory illnesses) lived within us and were transmitted when we touched, coughed or sneezed on each other.  

He noted that most transmission appeared to take place when people had “close contact” with each other – being within a few feet or so of each other. It did not take place over long distances in the way of the old miasma theory.  He guessed the “close contact” was because the germs were thrown out by droplets when people talked or sneezed on each other, although he expressly said we should not overgeneralize and that more study of the spread of germs through the air was needed.

This discussion of “close contact” primarily driving infection led to the six feet that we have seen today called a “safe distance”.  It was indirectly supported by a few early studies where people tried to colonize bacteria from sneezes but could not do so outside this “close contact” distance, although studies concluding the contrary seemed to be ignored.  Even Chapin knew from the late 1800s that smallpox could travel somewhat longer than this in the air, or that there were instances of spread beyond “close contact”. This could not be explained by droplets.

In the years that followed, further studies showed that bacteria could indeed float much further than “close contact” distances, but for some reason, the idea of close contact being caused by “droplets” thrown off by the infected person was sustained.  This was so, even though

a. in and around the 60s tuberculosis was accepted to be transmitted through small particle aerosols – proven by studies that showed infected people could infect guinea pigs on the roof of their patient rooms, connected by vents. 

b. later, in the 1980s, measles, formerly understood to be transmitted by “droplet”, was also accepted to be spread by smaller aerosol particles that could waft and float further than “close contact” distances, as it infected children at doctors’ offices an hour after the index patient had left.

c.  Chickenpox and flu were also often accepted to not simply transmit by “droplet”, mostly because of how contagious they were. 

However, overall, for some reason, the myth that respiratory illnesses were predominantly transmitted by droplets landing on the recipient, which has never been definitely proven by any study ever, persisted.  Most transmission did in fact occur within closer quarters, but this is explained by higher concentrations of aerosols at those distances.

Jonathan Mesiano-Crookston @/#COVIDisAirborne
Litigator & patent/TM agent. Biochem/pharm. MDC science & OBA equality committee

So as experts from different fields continue to argue about words, the COVID-19 crisis worsens and precious time is wasted. In order to define what is meant by ‘Airborne’ for a wider range of experts and laypersons alike, the following table was arrived at to clarify that in fact, per most common definitions, SarsCov2 is considered to transmit through the air, and not just within a ‘magical’ 2m radius.

Table 1 Differences between clinicians, aerosol scientists and the general public in the understanding of airborne terminology:

TermCliniciansAerosol ScientistsGeneral Public
AirborneLong-distance transmission, such as measles; requires an N95/FFP2/FFP3 respirator (or equivalent) for infection controlAnything in the airAnything in the air
AerosolParticle smaller than 5 μm that mediates airborne transmission; produced during aerosol generating procedures and also requires N95 respiratorCollection of solid or liquid particles of any size suspended in a gasHair spray and other personal/cleaning products
DropletParticle larger than 5 μm that rapidly falls to the ground within a distance of 1-2m from source; requires a surgical mask for infection controlLiquid particleWhat comes out of an eyedropper
Droplet nucleiResidue of a droplet that has evaporated to <5 μm; synonymous with “aerosol”A related term, “cloud condensation nuclei,” refers to small particles onto which water condenses to form cloud dropletsNever heard of it!
ParticleVirionTiny solid or liquid blob in the airLike soot or ash

Thermal Energy Design and Air Quality

Since the 1970s,  energy efficiency approaches and now net zero and zero-carbon emission design as sought to control heatloss through a range of envelope and ventilation strategies. The first approach consisted of making airtight buildings, which limited heatloss but then led to a buildup of CO2, indoor air pollutants and humidity, also known as SBS or Sick Building Syndrome. The second step, in the 1980s was to introduce controlled ventilation systems often with heat recovery (HRV/ERV) and in larger buildings DOAS or Dedicated Outdoor Air Systems (usually also with heat recovery cores and filters ie. This resulted in Indoor Air being purged of CO2, balanced humidity (30-50% RH) and reduction of pollens and other pollutants. MERV and HEPA filters further reduced pollutants and even mould and viruses. For a primer on ventilation systems, Health Canada has published a guide here: While HRVs are now mandatory in new construction (per OBC), most homes (including my own) do not have these systems. Incidentally, the onset of SBS begins at 800ppm of CO2 as measured in indoor spaces. Health Canada has suggested an upper limit of 1,000ppm, however the best practice is to aim for the closest approximation of outdoor air concentrations (~450ppm) with integral heat-recovery to limit energy waste.

The problem of Legacy Buildings 

New buildings are easy, we can design a ventilation strategy with filtration and heat recovery and we can measure in real-time CO2 and other indicators. But with existing building stock, we may not even have a ventilation system in place. Since we have inherited a wide range of buildings that we live in and occupy from every era of design and engineering, we must also have a strategy for first determining and then addressing air quality issues in our legacy building stock, whether they be homes, schools, offices or healthcare spaces. We propose to Measure, Ventilate and Filter, in that order.

Here is one example: As I write this, my own office measures 1445ppm of CO2. That corresponds to a rebreathed fraction of air of roughly 2.7%. I can see that outdoor air is currently 501ppm. My goal should be to get my office air to around 700ppm of CO2. Whoever built this place did not even put a ventilation fan in the bathroom. So I open a window, and within 10 minutes, I can get it down to 1053 – better. But now it is cold in here – should I crank my thermostat to bring it up to a comfortable level? No, not when I have a radiant ceramic heater beside my workstation: (see research blog on this below). As the Aranet4 updates itself every 5min, I can adjust the window from wide open to about 1/2″ – which over time it seems is enough to keep this one room of the house under 1,000 ppm of CO2. Fresh air check. Thermal comfort, check. But what if I am in a shared office? My next step would be to improve my whole house filtration by checking to see that my furnace filter has a new minimum MERV filter installed, and ideally, if I shared my office with anyone else I would be masking, distancing and filtering local air with a portable unit, such as the JASPR device we have been testing. As seen in the image gallery below, it has its own PM2.5 monitor, which in this case just spiked because we were cooking – it will quickly ramp up to top speed to clear the air of these particulates within 10 minutes. So best practices for indoor environments can and should consist of measuring CO2, Ventilating, and finally Filtering, on top of additional recommended public health measures. These kinds of solutions can be scaled to commercial indoor environments and classrooms as well.

Measure First

While I am not recommending architects step outside of their area of expertise, anyone (including architects) can educate themselves on IAQ/EAQ and purchase measuring devices to test their own homes, and potentially their client’s homes, and then share the results with their professional engineering colleagues to help develop solutions with, just as we do in our professional practice.

So what should an architect consider when examining an existing space, or planning a new one, when aiming for the best indoor air quality? Let’s begin with measuring CO2. For $300, a portable CO2 monitor ( can be purchased the provides an instant readout of CO2 in any space, whether it be a bus, car, school, hospital, classroom or bedroom.

There is a wide range of consumer and professional grade air quality measuring systems in the marketplace. We also use a building-integrated device called ‘Airthings‘ that provides data on CO2, Temperature, Humidity, Radon, PM2.5 and Barometric Pressure that feeds into a dashboard app. As a best practice, the OAA Headquarters in Don Mills is using the Airthings system, which verifies that CO2 levels were always within accepted norms. The building’s deep energy retrofit incorporated a 100% fresh air system with filtration and heat recovery. The system did however uncover an issue with low humidity (20%), that would not have been discovered otherwise, and that is subsequently being addressed. You can read more about this system in the blog linked below:

To keep it simple, we can just look to CO2 as a proxy gas for a wide range of other issues, from airchanges to occupancy to ‘Rebreather Correlations’ (chart below). We can also use CO2 levels as a general indicator of IAQ or Indoor Air Quality. For more recommendations on indoor air quality and metrics, Health Canada has also recently issued the following guidance:


Once we have measured the quality of indoor air in a given space, only then can we undertake a range of strategies for mitigating air quality issues, many of which can also reduce the transmission and persistence of the SarsCov2 virus in airborne aerosols and droplets. Post-intervention followup with subsequent measurements can confirm whether our strategy has been effective. To simplify even further, many HEPA units even have displays built in with IAQ metrics of one form or another, and Public Health Ontario has also issued guidelines or portable ventilation units: Measurement device companies have even integrated COVID-19 risk analysis into their platforms such as this:

David Elfstrom, P.Eng recommends this approach in any school considering a return of students:

Adequate Air Changes:

In order to assure proper air changes for a specific occupancy, professionals can refer to their professional guidance documents, but Public Health Canada’s recent guide can be a starting place: COVID-19: Guidance on indoor ventilation during the pandemic.

While measuring CO2 can help describe the ratio between indoor and outdoor air quality, it can similarly provide a benchmark for Air Changes per Hour or ACH. An ACH of 3 is recommended at a minimum to help reduce SarsCov2 transmission, with an ACH of 6 being recommended for congregate environments such as LTC, Schools and Healthcare. (need reference).

Conclusion: Educate, Measure, Ventilate and Filter.

  1. Education: Architects are at the front end of the design of almost every public building. To that end we urgently need to consider IAQ measures in the design of buildings, both in terms of the materials we use, the envelopes we design, but also the measurement and control of air in the systems that we coordinate through our professional engineer colleagues. Accepting the correct terminology and definitions of Airborne Transmission of SarsCov2 is a critical first step in identifying causes and developing solutions.
  2. Measure: It is now easier than ever to measure humidity, CO2, PM2.5 and Radon and subesequently to design systems that bring Air Quality to be within the range of accepted values as provided by public health agencies and professional standards.
  3. Ventilation: (with heat recovery where possible) As professionals trained in the science of thermodynamics, we are also obliged to consider the public health benefits of not only energy performance and carbon mitigation, but also Indoor Air Quality. Any building with a properly designed air-tightness and heat-recovery system will also bring the benefits of a draft-free and healthy home, that has increased co-benefits of increased durability, balanced humidity and lower operating costs.
  4. Filtration: In instances where there is inadequate capacity for improved ventilation, a strategy of filtering recirculated indoor air should be taken as a less-effective but nevertheless important way to to improve IAQ and infectious airborne particles. Filtration can be central (ie. Furnace and/or HRV filers) and local (room by room). Filtration can be considered like PPE for buildings. We can work to develop solutions to isolate airborne transmission by use of filters with or without ventilation strategies, even though ventilation is of greater importance. Public Health Ontario recently authored the following guide to Portable Air Filters (Jan 09, 2021):…/faq-covid-19-portable-air-cleaners.pdf?la=en)

Together with physical design for distancing and the design of ever more airtight structures with complementary natural and mechanical ventilation strategies for 100% fresh air, Architects can learn to measure IAQ with a range of readily available devices, and we can test spaces to see whether the buildings we have designed are within tolerance of the suggested limits for a range of these measures. Where IAQ can be improved, we can recommend a strategy of ventilation and filtration together with our engineering consultants. We can also provide guidance and leadership to our provincial governments where we feel that the design or use of spaces is inappropriate without well considered IPAC measures related to ventilation and filtration first being implemented wherever possible. It should be noted that the OAA has taken such action with respect to LTC homes in the province with this OAA Letter to MMAH re. inadequate IPAC measures in OBC. I feel that a second letter acknowledging the Airborne transmission of COVID-19 is also necessary, and one that our OAA membership can assist with in terms of advising on measurement, design, ventilation and filtration strategies over and above all current public health measures in all new and existing buildings.


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