It has been over a year since I have written anything here. I have been concerned with reading myself in the medical-scientific and public health literature about SARS-CoV-2 and Covid-19, because the deleterious consequences of this pandemic dwarf anything we system safety people have had to deal with during my career.

Many believe that engineers have much to contribute to this subject, and I am one of those who think so. The UK Safety Critical Systems Club has a Working Group on Covid-19, which I now convene, having taken over from Mike Parsons. The WG has a Covid-19 Working Group Page with meeting notes, essays (both original and links to others, under “News and Links”), and a series from me of Notes on Covid-19, with (currently) 22 parts, in which I have tried to annotate (what to me are) important medical-scientific/public health developments as they have occurred.

You don’t have to be a SCSC member in order to read the pages, but the SCSC does want you to register with your email address. (Scan the page down to “Notes from Peter Ladkin”). Some other essays of mine also appear there, and more are to come.

I wrote an essay on playing music in the time of Covid, and the issues around aerosols and ventilation, which appeared in Safety Systems Vol. 28 No. 3 in October 2020. I played outside in the garden over the summer with my flautist colleagues (the flute is one of the “worst” instruments for distribution of aerosols), but we had to stop in October when the weather got colder. I researched what I could do with my music room, and how effective it might be, and continued through winter. I kept coming back to the Technical Data Sheets of all the filtration/sterilisation devices on the market which I thought I could afford, incorporating ten-fold price differences, but didn’t commit to one, because I couldn’t figure out how to test it effectively in my environment (precise air circulation within the room is key). We simply didn’t play.

Until this weekend. On Sunday February 14, it was -18°C at daybreak and the snow piled up on my balcony to the depth that we could sculpt seats out of it, cover with a blanket, and eat cake in the afternoon sunshine. Six days later, on Saturday February 20th, it was 16°C in the sunshine and my music pal Inka and I played tunes. She came back Sunday to play some more, when it was 24°! I am sure it will get colder again — March often has deep frosts — but it was good to be able to play after five months of not doing so.

I am not the only one procrastinating about indoor air filtering. The issue with schools was solved in Germany by closing them in December. They will reopen this week. Changing the air in classrooms is as difficult as it is for music playing, and the issue of filtering has come up. There are many effective classroom-size filters on the market, along with results of commissioned studies on their effectiveness, and there is even government financial support. But there is apparently some resistance. A  report in my local newspaper, the Neue Westfalische, by Anneke Quasdorf on 2020-02-22, in German suggests that the North-Rhine-Westphalia state government set aside €50m for the acquisition of filters by schools, in Autumn last year. By the time the program ran out (in mid-January) only €12.5m had been given out. The city government in Bielefeld, where I live, apparently decided in November 2020 not to make use of them (and even to require schools that had acquired filters on their own initiative to shut them down). Quasdorf reports that the city government decided to look at the filtration issue again in late January 2021, and maybe apply for funding, but the program had ended (this seems like too much bureaucracy. Why stop such a program when it still has money left? Or why not reactivate it if there are late comers?).

A local manufacturer says they have delivered devices to schools “in three-figure numbers”, but they are locally not “authorised”. Their spokesperson points out that all it takes to “authorise” them is for the city to do so. There are studies that show that appropriate filtering is often more effective than the ventilation procedures recommended by the Federal Ministry of the Environment (here is one from manufacturer Wolf , and here is another, with more scientifically impressive graphics).

In my Safety-critical Systems Symposium Keynote talk on “Confounding Covid”, I mentioned HVAC (for Heating, Ventilation, Air Conditioning) as one of the key engineering areas, as well as dependable modelling. This short article by Ms. Quasdorf makes that case clear.

I am still figuring out how best to make available the video of my Keynote. In the meantime, there is an essay on Chances, Confidence and Risks Analysis (CCRA) applied to the risk of infection of child day-carers, and an explanation of a Simple Calculus of Confidence, used in the first essay, in the ScSS proceedings, under SCSC-161, Systems and Covid-19, the proceedings, on the SCSC publications page (viewing the page is open, but the individual pieces require that you register, as above).