Jamie's Notes

Aerosol Transmission of COVID-19 in Indoor Settings

El Pais has an interesting visualisation of how aerosol transmission works in indoor settings. It’s one of those things that you read and then wish you hadn’t because it makes the world just a little more terrifying.

Aerosol transmission is different from droplet transmission. The latter happens when someone coughs or sneezes at you. The droplets generally don’t travel far but infect if they come into contact with the eyes, nose or mouth. Aerosol transmission is by way of tiny particles, which are light enough to travel in air currents. They can stay in the air for hours, floating around and increasing in concentration until they are dispersed (or inhaled).

Silent / Talking / Shouting

It’s always seemed to me that aerosol transmission is understated in the UK response to COVID-19. Bars and restaurants have been allowed to remain open, and many people are now working in offices again – albeit with reduced numbers and preventive methods such as barrier screens and temperature checks. But if you’ve got an infected person in a room with 20 other people, with poor ventilation, none of the standard prevention makes any difference. The air will be full of aerosol droplets.

There’s still a couple of unknowns. We know that aerosol transmission happens, but we don’t know how much it is contributing to the wider spread. We know that ventilation helps, but we don’t know whether HVAC systems help or not.

The mitigation is straightforward:

  • Don’t stay anywhere indoors longer than you need to, ideally no longer than an hour
  • Make sure your destination is well ventilated, preferably through open windows/doors but at the very least through mechanical ventilation
  • Wear a mask when you can
  • Try to do things outdoors instead

Photos from 18th October 2020

Rendering LIDAR Data

I spent a bit of time this weekend learning how to render LIDAR data into 3D dioramas with Aerialod.

Aerialod is not the most intuitive program, but you can get some nice images out of it with a bit of experimentation.

Time well spent? Probably not. But it was fun.

Lake District

World Mental Health Day

Today is World Mental Health Day. Thanks go to Giles for letting me know, and for sharing his experiences.

‘Mental health’ was never a phrase that I’ve associated with myself. I’ve always thought myself to be quite resilient. I was, I thought, secure in my serenity and have taken pride in being able to work through situations clinically, rationally and logically. My wife, by the way, does not feel that this is an admirable quality.

My friend, Steve, took his own life this year. I hadn’t spoken to him for a while, and I had no idea he was suffering. My mother took her own life when I was ten. Mental health, whether our own or that of others, touches us all. Poor mental health can affect anyone. It is not a weakness, and we must talk about it.

Earlier this year, I started experiencing symptoms of what I later discovered was probably burnout. I felt anxious and couldn’t sleep. Basic tasks at work felt overwhelming. I was exhausted, and I hated my job. I felt a pang of dread on waking, and by the end of the week I was an anxious wreck. I reasoned that it would pass but I knew, or at least a rational bit of me knew, that I was heading to a bad place if something didn’t change. It was an odd feeling and I have never been able to work out the why of it. But I guess that’s the nature of these things.

I was lucky to have options. I gave up my job as a manager and took up a secondment elsewhere. I feel much better but it was a tough lesson to learn, because it means that I’m not as mentally hardcore as I thought. I am now much more sensitive to how I am feeling, and acknowledging those feelings as something real.

To those that are well: Reach out to your friends. Let them know that they matter and that you are thinking about them.

To those that aren’t: Talking helps. If you don’t have anyone that you can talk to, try your GP, or consider contacting one of the charities below:

Springhead Pumping Station

I had to take my car for its annual safety check this morning, so enjoyed a walk home along a couple of miles of the former Hull to Barnsley railway track. It was a blissfully quiet, the only other person on my route being a harried dog walker, minus her dog who had decided it would be more fun to go on a solo walkabout.

The route winds past Springhead Pumping Station – constructed in 1864 to provide the growing city with clean drinking water and still providing us with 25 million litres a day from the aquifer deep below.

I find buildings interesting. They raise a lot of questions. Who built it, and why? Why did they choose those materials and build it in the way that they did? Well designed buildings have the power to make you feel good about the place you are in, poorly designed ones do the opposite.

This is a beautiful building, constructed in red and yellow brick with large arched windows and an octagonal lantern perched atop a square tower. It was once open as a museum but closed when Yorkshire Water became paranoid about poisoning of the water supply, and nowadays it’s surrounded by vast amounts of fencing and enormous security gates. It would once have been visible for miles around, but it’s impossible to get a good look at the building now.

This picture from Chris Pepper shows it from inside the grounds:

Credit to Chris Pepper

The Victorians didn’t mess around when designing municipal buildings.

Eddie Van Halen: 1955-2020

Letters from Nominet

Many moons ago, Nominet, the UK domain registrar, confirmed the registration or renewal of your domain with a physical letter. I remember being very pleased to receive mine:

I have a hazy memory of them sending me a certificate on first registration, but I can’t find it anywhere so I could be making that up.

They must have been sending out thousands of letters a day, and I assume it was an admin nightmare because it took them three months to send me this letter. Shortly after this they moved to an online system, and this was the last one that I ever received.


Feed Blacklight with a website and it’ll scan it and tell you what tracking technologies are being used.

I scanned a handful of the websites that I visit daily. One site had 16 trackers in operation and placed 30 third-party cookies! Almost all of them told Facebook and Google of my visit.

I was surprised to see that Google is setting third-party cookies via my site – probably as a result of me embedding Youtube videos.

More in the archives.