Ventilation project

Lower down the page is an explanation of how CO2 is a proxy way to measure how good ventilation in a space is. This is the scale I’m going with for the new CO2 monitor:

  • 400 to 420: Outdoors
  • 600 or under: Excellent
  • 601 to 800: Good
  • 801 to 1000: Fair
  • 1001 to 5000: Poor

New monitor readings

I’ve acquired a newer, more accurate CO2 monitor, that can store up to 5 days of data in it. I’ve thus found that the previous monitor was a little bit… optimistic. (But at least did rise and fall at about the same pace the new one did, so was detecting CO2 changes.) I’ll still keep the old data there for now, at least until I have new readings for those places.

OutdoorsPublicNo415Outdoor calibration of this monitor
HerrlesFarm market (indoors)Moderate477 to 698; Average 579Excellent (on average)
Sobey’s LaurelwoodGrocery storeModerate612 to 659; Average 640Good
Laurelwood Family DentistryDentist officeWaiting room: No
Exam room: Yes, given space
Waiting room: 509 to 635
Exam room: 668 to 872
Waiting room: Good
Exam room: Fair to Good
But, both spaces had large HEPA filters cleaning the air of particles, making the ventilation readings less significant.
(Staff were also in N95s.)
Shopper’s Drug Mart, LaurelwoodPharmacyModerate612 to 667; Average 639Good
375 Hagey BoulevardOfficeModerate437 to 461; Average 452Excellent
Global Pet Foods, LaurelwoodPet food storeNo500 to 530; Average 522Excellent
Mazda CX5CarModerate1241 to 2254; Average 1836 (recirculate)
1056 to 1680; Average 1293 (outdoor air)
And you see the effect of the fan setting. With the recirculate setting, it kept getting worse.
Cycling outdoor air in, it kept getting better.
Both were short drives. Windows closed for both.
Home Depot, WaterlooHardware storeModerate474 to 659; Average 593Excellent (on average)
Absolute Hair StudioHair salonModerate1008 to 1332; Average 1291Poor

Older monitor readings

The reported CO2 levels were probably all a little higher than reported here, given the quality of the monitor. Have now removed the ones I’ve re-measured more recently.

SpaceType Crowded?CO2 levelComments
The Winery Restaurant at Peller EstatesRestaurantNo; we were the only guest (except at the very end, when two other people were seated)407It just stuck at this excellent reading the whole time. Large empty room, high ceiling.
Loloan Lobby Bar RestaurantNo, one other couple there at first, one more couple a bit later420This is incredibly good ventilation for an indoor space! It stayed at this really low level the whole time.
This space is further enhanced with filtration, in the form of Hepa filters (out where we could see them).
Laurelwood Veterinary ClinicAnimal careNot especiallyNot measured!But still noting as they did have HEPA filters in all the rooms, which is bound to help. As well, all staff were in N95 masks (well past date any masks were required).
Centre in the SquareConcert hallNot very full in general (it can seat over 2000), but our area was pretty crowded.410 to 445This is very good. It dropped to 410 as we arrived (was higher in our car) and stayed there for about the first hour, then crept up slowly for the remaining 45 minutes of the show, but stayed at a low level. It’s an older building with a very high ceiling.
The Olive BoardRestaurantNot filled but we did overlap with other patrons420 to 450Another eatery with excellent readings! It did bounce around a bit but never above 450, that I noticed.
Treadwell CuisineRestaurant covered patioDefinitely other people were seated on the patio, but the tables weren’t crowded together450ishI was just curious how it would read given that it was more outdoors-ish, and we were seated beside a heat lamp. It did bounce around, from around 420 to 470, I’d say.
Waterloo West OptometryHealthcare settingOne other client in waiting area480 (waiting room) to 630 (exam room, door closed)Some bouncing in waiting room, but it sort of settled around 480. Couldn’t check it regularly in the exam room due to having my eyes checked, but looked at it right after leaving and it was measuring 630.
Both are pretty good (newer building), but does show the effect of the waiting room being closer to a door regularly opening to the outside.
Timmins AirportAirportYes520This is in the waiting area past security. It has doors opening to the outside, because in Timmins you walk out onto the tarmac to board the plane.
Dining area at The Oban InnRestaurantNo, one other couple besides us550ishThis one bounced around, too, but from low 500s to low 600s.
Princess Twin CinemaMovie theatreNot overly. About 20 people there.500 to 810The readings bounced around quite a bit, going up, then back down. Likely whenever the air exchanger ran, it would fall, then creep up again, and repeat. The average levels did gradually increase throughout the 2.5 hour movie, though—wouldn’t fall as low as previous, then would rise higher. By the end the highs were a little above 800. I feel like it started with an average of 550 and ended more around 675 (but my device isn’t fancy enough to do any analytics).
My carPrivate vehicleOne or two people600 to 850+CO2 in the car really rises when the windows are closed and the fan isn’t running.
Once the fan gets going, it’s a noticeable improvement.
Opening windows makes the level even better.
Public equivalent: a taxi
(Not taken these measurements myself, but seen reports that trains measure around 1500, which is terrible, and buses can be even higher…)
The Oaklands at the Riverbend InnRestaurantNo; we were the only guests700ishOne of those rooms where the CO2 levels bounced around a lot, from the mid-600s to over 800. So apparently not terribly good ventilation, as it certainly was not crowded.
Festival Theatre, StratfordLive theatreYes, full house1550 (intermission), 1690 (end)Didn’t watch the monitor the whole time, but checked it at these points, and wow, that’s a lot of CO2.
Would note their website says they have “updated our air filtration system”—and filtration can remove virus particles without lowering CO2 levels as ventilation does.
Still, I’d keep a mask on here…

Site for reporting your own CO2 measurements, and for looking them up:

Background on Co2 measurements

As we shift more into the “it’s everyone for themselves” phase of the pandemic, one important piece of data is how well-ventilated indoor spaces are. It’s particularly important for places where you can’t mask, like restaurants, or where it’s particularly uncomfortable to do so, like for intense gym workouts.

Covid-wise, of course, this matters more when case counts are higher, and the spaces are more crowded. But cleaner indoor is generally beneficial to your health. It’s just not something we gave much thought to before Covid.

It’s something governments need to tackle, ultimately—measuring indoor air quality, improving it in spaces they control, putting in place measures to encourage (or require) private companies to improve it as well. I plan to ask political representatives and candidates about this.

But what to do in the meantime? I’ve decided to invest in a portable CO2 monitor. And I’ve started bringing it with me to public places.

CO2 is just a proxy measurement for poor air. CO2 itself, unless incredibly high, doesn’t pose an immediate danger. But CO2 levels staying at higher levels indicate that the space isn’t very well-ventilated—it’s not doing a good job of replacing the indoor air (full of people’s COs exhalations) with cleaner air from the outdoors. (Assuming here outdoor air of generally good quality, that there’s no forest fires nearby or smog advisories.)

Credit to

By the way, masking has no effect on measured CO2 levels, because it’s such a light gas, it just passes through masks. (Virus particles are larger.)

One more note: Fixing ventilation can be time-consuming and expensive in some cases. In the meantime, you can improve the situation by deploying portable HEPA units. These can (possibly) help clean virus from the air, but they do not reduce the amount of CO2. But if two spaces have high CO2, the one that has portable HEPA units or similar, like Corsi-Rosenthal boxes, is a better gamble.

Credit to

Masking post-mandate

Thought I might also note my experience with this, weeks 1 and 2:

  • Sobey’s Columbia: 80% of staff and customers masked
  • Shoppers Laurelwood: 100% of staff masked, 80% of customers
  • Brady’s Deli: 0% of staff masked, 20% of customers
  • Starbucks Laurelwood: 100% of staff masked, 80% of pickup customers
  • Global Pet Foods, Laurelwood: 66% of staff masked (2 out of 3), 100% of customers
  • Oban Inn, Niagara: 100% of staff masked
  • Trius Winery, Niagara: 100% of staff masked
  • Strewn Winery, Niagara: 100% of staff masked
  • Peller Estates Winery Restaurant, Niagara: Staff not masked
  • Oaklands at the Riverbend Inn, Niagara: Staff not masked
  • Treadwell Cuisine: 100% of staff masked; vaccination proof required
  • Canadian Tire: 0% of staff masked; 75% of customers

Percentages just estimates, obviously—well, except the 0% or 100% of staff, which was easy to assess.