Wednesday, October 28, 2020

Get an Air Purifier for Christmas

Christmas is coming, the great get-together time of families and friends. 

This is the very last thing that epidemiologists and medics want to happen in terms of the Covid-19 pandemic. 

There will be advice from Government on how many family members are allowed to get together, for how long and how close.

The bedrock advice of Hands, Face and Space will remain valid.

Many people (let's call them the Wise Virgins) will adhere to the official advice. Some (let's call them the Foolish Virgins) will not, and will have large Christmas gatherings at work and at home where many will become more or less rat-arsed, and forget the rules.

In both groups, virus will be transmitted; more so in the case of the Foolish Virgins but the inescapable fact is that if the number of people sharing air in a room goes up, so too does the probability that virus will be transmitted from person to person.

It is impossible to eat a Christmas dinner with a mask on, and people will be laughing, shouting and even singing. Droplets will be exchanged, and there will be a spike in cases in the first week of the New Year, and, sadly, a spike in deaths in late January.


There is something we can do to reduce the probability of these spikes.

We can of course have Christmas dinner outside, but let's face it, very few if any will do this.

We can also open all the windows and keep the air moving through the house. Some will do this, but, let's face it, not everyone will.

There is something else that we can do, comfortably.

Let's take the case of a family of Wise Virgins  sitting around the table eating their Christmas dinner. The oldest boy, let's call him Colin, has just come back from Uni. He had a private test last week, and it came back negative, but unknown to him, five days ago one of his flat mates coughed over him and now he is an pre-symptomatic carrier. Not a lot, (virus shedding is maximal on the day symptoms start) but he is indeed putting out droplets containing Sars-Cov-2 virus (the virus that causes Covid-19 disease).

In the centre of the dinner table, hanging above it next to the table lamps, is a piece of technology called an Air Purifier. It is drawing in the air above the table, and passing it through a HEPA (High Efficiency Particulate Absorbing) filter, combined with a variety of other processes depending on quality.

A large part of the virus particles chucked out by Colin will be trapped and killed in the Air Purifier. Instead of landing on the table, or hanging about in the air, or drying out and drifting as aerosols up the stairs into the rest of the house, they are safely trapped and die in the filter of the purifier.

Not all of them. Most of them. There is still a risk of transmission, but the Air Purifier reduces the probability of others round the table and in the room getting enough of a loading dose to get sick (the size of the loading dose is proportional to the severity of the subsequent illness).

It is all about probability. Nothing is black and white. Perfection is not on the agenda. Colin may forget his distancing, and may play with the 6 year old, who may get Covid. But the probability of transmission in a house with clean air is lower than it would be if the air is laden with Colin's virus.

The same goes for a family of Foolish Virgins. In aggregate, the spike in C19 cases will be less in houses that use Air Purifier technology.

Air purifiers are available widely. They cost anything from £40 to £700, but you can get a decent one for about £130 inc p+p. I like the Blue Air Pure 411 because it is very low wattage (1.5-10W). 

I am not on commission. I am writing this because I believe this technology will save lives and will ease the burden on my colleagues in hospital. I also believe that air management technology applied in many other ways will enable us to live far more normal lives than we otherwise would. Manufacturers will not claim that their products are guaranteed to stop people getting Covid, and of course we will hear the usual nonsense about how using air purifiers will make people stop wearing masks and washing their hands, but this kind of conservatism is inevitable for any innovation.

Buy one. Use it. Stay well, stay safe.

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