Hi all,

Having promised a weekly newsletter, of course I fall short at the first hurdle and this weekly newsletter is now coming out over a week late. Such is the hubris of over-enthusiasm. When will I learn?

But before I get onto Part 2 of the epic series on improving the air in our local Pilates studio, a few news items this week.

Europe and North America are heading into the next COVID wave (the eighth global?) with multiple immune-evasive variants, led at the moment by BQ.1.1, a derivative of BA.5. Best to look at hospitalisations, as cases are not reliably reported anymore. UK hospitalisations are up 48% week on week, with a doubling time of less than two weeks.

You can see the upticks across Europe here and experience tells us that these waves are global, so there is no reason to believe Australia will not see another wave before Christmas:

Dutch schools now have compulsory CO2 monitoring, while Australian schools still refuse donations of CO2 monitors. Meanwhile, we know that, as CO2 levels double, the risk of transmission of airborne infectious diseases also roughly doubles.

Actuarial estimates of Australian excess deaths in June are reportedly looking worse than the five months to end of May when they were at 12% (8,500 excess deaths):

Keep an eye on Karen Cutter’s Twitter account for the June actuarial estimate of excess deaths, which is likely to be published on Thursday, October 6th. The actuaries have no agenda beyond providing accurate information for the insurance market: BELIEVE THE ACTUARIES.

On the excess deaths theme, the Singapore Ministry of Health published a couple of weeks ago that all non-covid excess deaths were accounted for by deaths within 90 days of covid infection. Given the increased rates of vascular disease post-covid, this is no surprise. Karen dissects the details here.

And “immunity debt”? Have you come across that? The notion that lockdowns prevented people being exposed to infections, so now they have an “immunity debt” and are being infected more as a result. It makes no sense, and guess what: it was invented for the pandemic. @TRyanGregory points out that there are only ten references to it on PubMed, and none before August 2021.

Adventures of a CO2 Guerrilla in the Pilates Lion's Den, Part 2

Anyway, enough of this hilarity, and on to Part Two of our epic series. To recap: in Part One, fearless CO2 Guerrilla and woman in lycra, @CallMeSafetyMom, took it upon herself to improve the air quality in her Reformer Pilates studio, identified as seriously deficient.

The manager of the studio has proved receptive, a preliminary discussion has been had and an Aranet4 CO2 monitor lent out. Now, fast forward a couple of days and I drop by to help her pair the monitor with the Aranet app on a smartphone.

Manager is at the reception desk, chatting to the receptionist, no-one else in the waiting room. The Aranet4 is sitting on the desk, reading 1100ppm CO2; far too high, especially with such sparse occupancy of the space.

She smiles as I approach:

“We’ve been watching it climb. It goes up quickly. We had no idea!”

“Uh, yup, we humans are pretty effective CO2-making machines.”

“I’m glad you’re here. We were just about to order another HEPA filter. What do you think of this one?” [Points to the computer and shows me one with an ionising function.]

“NOPE! You just need a straight filter. The ioniser is a waste of time at best and harmful at worst. And also that filtration rate probably isn’t enough.”

I get them to pull up the Clean Air Stars page. Clean Air Stars is a non commercial, not for profit organisation, set up by Melbourne anaesthetist, polymath and all round nice guy, Dr Pieter Peach, to help businesses around the world improve their indoor air quality. We go straight to the air filter recommendation tool:

Before we go on, let’s remember what we’re trying to achieve. This PIlates studio has unacceptably high CO2 levels, indicating that participants are rebreathing each others’ expired air to a degree which puts them at significant risk of contracting an airborne infection, such as covid, if there is an infected person also in the room.

In other words, the ventilation is inadequate: there isn’t enough fresh air getting in to replace the air people have just breathed out. This is a windowless 1980s building and the opportunities to increase the amount of fresh air getting in are minimal, so what are we going to do to make the indoor spaces safer?

The only thing we can do is to filter the inside air, which will remove all infectious particles and also allergens like house dust or pollen. It’s important to note, however, that it will not reduce the CO2 level at all. That’s OK, though, because in infection terms the CO2 level does not matter one jot. In terms of cognitive function, it does, but luckily straight leg raises are not as taxing on the old cerebrum as doing long division or memorising Shakespeare.

Now, let’s look at the air filter recommendation tool itself. Most of it is self-explanatory and if you’re reading this you’re smart enough to figure it out, but I want to draw your attention to the two ways which Pieter has given you to calculate the amount of filtration you need for your space.

One way is by calculating the amount needed to achieve six air changes per hour, which requires you to calculate the approximate room volume:

The other way is based on the number of occupants in the room:

Why is it important to have two ways to measure required amount of filtration? Because it’s not an exact science and air changes per hour becomes less meaningful in a larger room with very few occupants. In our case, we used the filter to calculate filtration required for six air changes per hour and also per occupant at 50 litres per person per second and they came out roughly similar.

The tool showed us that three medium sized HEPA filters for the main exercise room would provide the required filtration to make it safe and cost about 1200 Australian dollars. Adding small filters for the two consult rooms, reception and the loo would cost about the same again. At the time of writing, these devices are on order.

A couple of quick points to make:

Appropriately sized HEPA filters take about 15-20 minutes to clear a space of existing particles, so you can't switch them on and expect them to be protecting you instantly.

Also, they will protect you from dispersed, free floating particles, but not from near field transmission. In other words, if an infected person coughs right in your face a HEPA filter won't save you. You need to wear a good N95 - layers of protection, remember?

If you have questions about choosing HEPA filters, please address them to Pieter. He is literally one of the world experts on this topic and knows far more about it than we do.

And, finally, in the spirit of “living with covid”, we have decided to “live with” even lower margins, by giving existing customers and subscribers to this newsletter a discount of $10 per order on the 3M Aura N95 respirator masks which we sell.

I will not take a breath in an indoor space outside my home unless I am wearing a 3M Aura. We know these are expensive for ordinary people, but they provide excellent protection and we want to get them out there and being used.

So, if you want to do the best you can to protect yourself from all airborne infections, including covid, click on the picture below and enter the discount code "stay healthy" at checkout for your $10 discount per order, valid until October 18th:

Hasta la vista, friends, until the next weekly (I know, I know!) newsletter,

David

P.S. Final bonus this week: my thoughts on the oxymoron of "mild hospitalisations". Give me strength.