[Reporter: Ioanna Roumeliotis] At a boxing club
it's all about staying on your toes.
And these days keeping up with an invisible opponent.
Here they're fighting COVID-19 one jab at a time.
Where I'm coming from is that as a business owner
it's in our best interest to do everything we can.
[Reporter] From temperature checks to limiting capacity and the usual masks
owner Brian Castillo is doing all that and more.
Not only does the equipment at his nine round club in Toronto
get disinfected non-stop, so does the air.
So if you come on down here with me
what I'm going to show you over here is going to be our HVAC system.
[Reporter] Castillo has installed a gadget to his ventilation system
and he says it's as close to a knockout punch as it gets.
We put in this little device here which makes a dramatic difference.
It's a UVA filter and what it does it actually sends out UV light into the duct system
which kills mold, bacteria, pathogen and viruses.
It'll purify the air up to 99.99 per cent.
[Reporter] As a member of a provincial sports organization
his club has remained open in a limited capacity under its guidance.
And Castillo says he can't afford to take any risks.
Why did you do this?
Why take the extra step?
Our livelihoods depend on this.
So what I was doing is just following along in other countries
that are actually doing well and what they're implementing
and what they're doing and what some gym owners have basically shared
and said what works.
And what they're saying is a simple little device like this is doing the trick
and this is something that I did myself to ensure that my clients have the best facility possible.
[Reporter] The idea is to kill COVID particles in the air before they're inhaled.
Not just virus found in big droplets like when people sneeze
but in tiny ones too called aerosols.
Those are expelled by simply talking.
There is growing evidence those aerosols can travel well beyond a six foot distance
and linger in the air.
It could be a few minutes, it really depends.
It could be a few seconds and someone has the the time to inhale it
and it could be hours and we know that some particles will remain airborne forever.
They will never settle down so it can be from a few minutes to forever.
[Reporter] Caroline Duchenne is a professor at the Université Laval in Quebec City.
She's also a bio-aerosol expert.
These images were taken early in the pandemic
when she and her team started taking air samples from outbreak settings
like hospitals and long-term care centres to study how COVID-19 can spread in the air
in aerosol form.
When the pandemic started, I remember reading several reports about people wondering
if it would be possible to catch the virus outside
when walking beside someone who has the disease.
And I think with the air movement and the very rapid dilution of the contaminants
outside it's not a very big issue but for indoor air ventilation has to be addressed
as a major part of the infection control.
And there is more and more evidence that the major outbreaks
and the super spreading events that happened so far happened indoor
in poorly ventilated spaces.
[Reporter] Those super spreader events have been scrutinized from the start.
One of the earliest ones in a restaurant in China in January.
An infected person at table A who did not have symptoms
not only spread COVID to four people at the same table
but to five customers at surrounding ones.
The theory is air conditioning currents move the contaminated particles
across the room.
Since then several more case studies found the same alarming evidence
prompting 239 scientists from around the world
to write an open letter to the World Health Organization in July
urging the agency to recognize that airborne transmission of coronavirus
by smaller aerosol particles is possible.
Duchenne was among those who signed that letter to the WHO.
Why was that important for you to do that?
I think when people start speaking the same language
then it becomes obvious that ventilation has to play a role.
So this letter was really to bring that to the attention of the decision makers
and policy makers that this aspect of the transmission control was neglected so far.
The WHO officially recognized the risk shortly after.
The U.S. Center for Disease Control and Prevention did the same in September.
The Public Health Agency of Canada just followed suit last week.
We thought the quality of the air was a factor that we wanted to at least address.
[Reporter] But James McKinnon acted well before that.
McKinnon is the principal at St. Michael's College School in Toronto
and for months he's kept track of what the science has been saying about aerosols.
We're listening to anybody who wants to share with us new ideas
but at the end of the day it's really about mitigating risk
and we felt that it was a worthwhile direction to go to
to really keep our staff safe as well as the students and their families when they go home.
[Reporter] The school has taken every precaution, hand washing stations
thermal body scans, masks and distancing.
Clean air was also a priority so the school invested in that too.
My understanding of the units that we have certainly is that
there's a 99 percent kill rate for bacteria and viruses
including COVID so the standard's quite high.
Our units recycle the air in a classroom anywhere from five to ten minutes.
[Reporter] That's a pretty significant measure to take.
We think so but we think it's worthwhile.
I mean we will do what we can.
We also have work to do around keeping them connected at school and learning at school.
We know the value of trying to keep schools open so
we'll do what we can to make that happen.
Keeping the windows open helps
but public schools are also trying to do more to improve indoor air quality.
There is government funding earmarked for ventilation
but with so many aging school buildings, upgrades will take time.
This recent donation of portable air purifiers is a welcome fix.
Hundreds of the units have been distributed to schools
in communities with higher COVID rates.
This helps a great deal
because we'll be able to put an air purifier in every single one of our classrooms
with kids so that's going to definitely help us throughout the winter.
[REporter] Gord Young is the principal at Charles Z Webster public school in Toronto.
His school was the first to get the donated air purifiers.
We've been looking at our air quality since before we came to school
and that was one of the big concerns because it's an old school
and so we're opening the windows right now but the weather's changing.
And so we're gonna eventually have to close the windows
so this is a really important piece to the puzzle.
[Reporter] Back at the club the fight against COVID is in the early rounds
and Castillo says he's bracing for more.
Always rather err on the side of caution.
If there's precautions we can take we'll take them
even go above and beyond if we have to
mainly because the data is changing.
I'd rather go above and beyond and ensure that we're doing the appropriate things
than feeling overconfident, maybe slacking a little bit.
[Reporter] Because with so much at stake he says he can't let his guard down.
Ioanna Roumeliotis, CBC News, Toronto