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Why don’t we just open the windows? Covid-19 prevention lost in translation

bmj.com

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Re: Why don’t we just open the windows? Covid-19 prevention lost in translation

#41

Post by newaccount74 »

323 wrote: post #28

Ventilation is energetically expensive, and can be even impossible to retrofit (windows that don't open, ...) Purification however is energetically very cheap (just a fan blowing through a filter, maybe with a UV led, no temperature change). And has the bonus benefit of removing other dangerous particulate stuff from the air (dust, smoke, ...)

Heat exchangers can recover a large fraction of the energy lost through ventilation. Modern systems can even recover humidity from the air leaving the building.

Air purifiers are very loud and mostly effective at removing particulates. If you want to remove VOCs, formaldehyde and CO2 then ventilation is a lot more effective.

A well designed ventilation system can be completely inaudible.

Re: Why don’t we just open the windows? Covid-19 prevention lost in translation

#42

Post by newaccount74 »

Madmallard wrote: post #32
chillwaves wrote: post #5

Earlier quoted context omitted.

There is also a problem of comfortable humidity levels. If you just have open windows, it seems like you will have very dry air. There are modern solutions for air exchanges that do retain some of the heat and moisture while allowing for fresh air to ventilate the indoor space. https://www.explainthatstuff.com/heat-recovery-ventilation.h...

? If your windows are open you will trend toward outside weather. If you’re in a dry climate then yeah it’ll be dryer but the reverse is also true. Outside air is far better than inside nearly everywhere in the world

Cold air can hold a lot less water vapor than warm air. If you open the window when it's cold outside, then the air will become very dry as it heats up.

So even if you have 80% humidity outside on a cold winters day, once that air gets inside and heats up to room temperature it's going to be like 20% humidity.

Re: Why don’t we just open the windows? Covid-19 prevention lost in translation

#43

Post by nawgz »

WithinReason wrote: post #27
delecti wrote: post #25

Earlier quoted context omitted.

For better or worse, the medical community is usually hesitant to recommend things before studies have been done, and some "common sense" advice is difficult to test.

Masks have been recommended heavily since the beginning without good evidence that they are effective. [0] https://www.medrxiv.org/content/10.1101/2020.03.30.20047217v... CONCLUSIONS Most included trials had poor design, reporting and sparse events. There was insufficient evidence to provide a recommendation on the use of facial barriers without other measures. We found insufficient evidence for a difference between…

Weird to pick a release from March 30, 2020. A modern review[0] concludes:

Our review of the literature offers evidence in favor of widespread mask use as source control to reduce community transmission: Nonmedical masks use materials that obstruct particles of the necessary size; people are most infectious in the initial period postinfection, where it is common to have few or no symptoms (45, 46, 141); nonmedical masks have been effective in reducing transmission of respiratory viruses; and places and time periods where mask usage is required or widespread have shown substantially lower community transmission.

The available evidence suggests that near-universal adoption of nonmedical masks when out in public, in combination with complementary public health measures, could successfully reduce Re to below 1, thereby reducing community spread if such measures are sustained.

[0]: https://www.pnas.org/content/118/4/e2014564118

Re: Why don’t we just open the windows? Covid-19 prevention lost in translation

#45

Post by legulere »

323 wrote: post #28

Ventilation is energetically expensive, and can be even impossible to retrofit (windows that don't open, ...) Purification however is energetically very cheap (just a fan blowing through a filter, maybe with a UV led, no temperature change). And has the bonus benefit of removing other dangerous particulate stuff from the air (dust, smoke, ...)

Automated ventilation saves energy. You don’t need to open windows anymore which leads to less heat or cold coming in. If your ventilation system has a heat exchanger it’s performing even better. It’s impossible to build highly efficient houses without automated ventilation.

Re: Why don’t we just open the windows? Covid-19 prevention lost in translation

#46

Post by mikeyouse »

adventured wrote: post #24
KevinEldon wrote: post #6

Earlier quoted context omitted.

You’re volunteering?

It's trivial to get volunteers. I'll volunteer. In the US we're around SARS2 spreaders all the time. Every time you spend ~30 minutes walking around in a major retail store chain you're highly likely to be exposed to SARS2. Now do that N times per week like most Americans have been for the past year plus. What am I supposed to be afraid of compared to that? I've had Covid; early into the pandemic. It was quite unplea…

I'm not sure how you're parsing out those 100k people that wouldn't have died had we had vaccines earlier since we can't get tens of millions of people to take the live-saving free vaccines that have been available for nearly a year now.

Challenge trials are fine but were hardly needed when we had unchecked spread of Covid for bog-standard RCTs. The historic speed that the vaccines made it through FDA approval were in large part due to the millions of active infections all over the country and world such that you could see the control vs. experimental groups very easily.

Re: Why don’t we just open the windows? Covid-19 prevention lost in translation

#47

Post by calsy »

323 wrote: post #31
nicoburns wrote: post #4

This agrees with my intuitive impression of everything I've read on Covid-19: that the primary transmission vector is through the being in unventilated or poorly ventilated enclosed spaces with an infected person for ~15 minutes or longer. I definitely feel like neither governmental policies or people's individual precautions and behaviours quite reflect that reality.

There have been documented cases of infections happening in seconds. Yes, longer exposure time increases infection probability, but the 15 min threshold is arbitrary, like the 2 meter social distancing. A bit like the "you can pick up food from the floor if it sat there for less than 5 seconds" meme.

How are infections measured in seconds?

Re: Why don’t we just open the windows? Covid-19 prevention lost in translation

#48

Post by mlyle »

nicoburns wrote: post #4

This agrees with my intuitive impression of everything I've read on Covid-19: that the primary transmission vector is through the being in unventilated or poorly ventilated enclosed spaces with an infected person for ~15 minutes or longer. I definitely feel like neither governmental policies or people's individual precautions and behaviours quite reflect that reality.

I'm a teacher at a school.

- We eat outside.

- We have filters upgraded to MERV-13 and the fans run the entire school day.

- We have windows and doors open on all classrooms, except for A) a few that don't open outside, or B) when it's rainy/windy to the point it's not possible. We have small, secondary HEPA filters that we run in those circumstances. (Often, we're blaring AC or heat into a room with all doors and windows open just to get a few degrees closer to comfort).

- We mask indoors, too.

So far, no secondary cases attributable to spread at school. We've had frequent testing for much of the time, too, so they'd likely get detected. Now a lot of the student body is vaccinated, too, but this dates to before that.

Re: Why don’t we just open the windows? Covid-19 prevention lost in translation

#49

Post by WithinReason »

jonstewart wrote: post #39
WithinReason wrote: post #27

Earlier quoted context omitted.

Masks have been recommended heavily since the beginning without good evidence that they are effective. [0] https://www.medrxiv.org/content/10.1101/2020.03.30.20047217v... CONCLUSIONS Most included trials had poor design, reporting and sparse events. There was insufficient evidence to provide a recommendation on the use of facial barriers without other measures. We found insufficient evidence for a difference between…

This paper’s from March, 2020?

Note that I said "since the beginning".

Re: Why don’t we just open the windows? Covid-19 prevention lost in translation

#50

Post by sharperguy »

A metaphor I was thinking of earlier.

If a guy is going to piss on you, you're going to be happy if he has to keep a pair of speedos on as he attempts it. You could also just move further away from him.

But if you're both swimming in the same pool while he pisses in it, those speedos will make little difference anymore. Neither will your distance from him help very much.

What will help much more is the amount of water in the pool, and the amount of fresh water being pumped in and old water pumped out.

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