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The experiment that proved airborne disease transmission

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Re: The experiment that proved airborne disease transmission

#51

Post by amluto »

lifeisstillgood wrote: post #23

UV-C lights that irradiate an air duct is literally the most surprising (and in retrospect obvious) thing I learnt today. Is this something a household HVAC could be upgraded to. Do HNers in areas that have air con think it's a "yeah people will want that" idea?

Nope. I would much rather have a good filter than mechanically removes infectious particles, wildfire smoke, and particulates in general.

For a residential recirculating system, the relevant parameter is flow rate times fraction of particles removed in one pass. An AC or heater generally has a high flow rate and needs a filter to keep the heat exchanger and fan clean regardless. The added material and energy cost of a good filter is low.

On the other hand, if you are moving air from one space to another and don’t want to contaminate the space you’re moving air to, the absolute filter / sterilizer efficiency may matter. Things like HEPA may be useful here.

I would be surprised if a UV lamp is cost effective for new installation. For retrofit in a system that can’t handle a better filter, maybe.

Re: The experiment that proved airborne disease transmission

#52

Post by vimax »

ajb wrote: post #32

Ok, dumb idea time: suppose that everyone in an office sits on a chair that raises their body to X volts. At the same time a collector mesh is provided at each desk, at -X volts, but shielded so that you can't touch it and shock yourself. What X is large enough to ensure that all the virus particles you cough out end up at the collector? Is it possible to do this without electrocuting everyone?

that sounds kind of like what an ionized air purifier does

Re: The experiment that proved airborne disease transmission

#53

Post by imposterr »

ajb wrote: post #32

Ok, dumb idea time: suppose that everyone in an office sits on a chair that raises their body to X volts. At the same time a collector mesh is provided at each desk, at -X volts, but shielded so that you can't touch it and shock yourself. What X is large enough to ensure that all the virus particles you cough out end up at the collector? Is it possible to do this without electrocuting everyone?

Free electrons tend to distribute themselves on an object as to minimize the repulsive forces between them. This usually means that they distribute evenly on the surface of objects.

Humans are a bit more complicated in structure than say a metal ball, but my guess would be that there would be a similar situation where all the free electrons would just build up on the skin. Therefore, I don't think the particles one would cough up would be negatively charged.

Re: The experiment that proved airborne disease transmission

#54

Post by enchiridion »

imposterr wrote: post #53
ajb wrote: post #32

Ok, dumb idea time: suppose that everyone in an office sits on a chair that raises their body to X volts. At the same time a collector mesh is provided at each desk, at -X volts, but shielded so that you can't touch it and shock yourself. What X is large enough to ensure that all the virus particles you cough out end up at the collector? Is it possible to do this without electrocuting everyone?

Free electrons tend to distribute themselves on an object as to minimize the repulsive forces between them. This usually means that they distribute evenly on the surface of objects. Humans are a bit more complicated in structure than say a metal ball, but my guess would be that there would be a similar situation where all the free electrons would just build up on the skin. Therefore, I don't think the particles one w…

Would the particles get charged as they pass through the later of electrons?

Re: The experiment that proved airborne disease transmission

#55

Post by computator »

ajb wrote: post #32

Ok, dumb idea time: suppose that everyone in an office sits on a chair that raises their body to X volts. At the same time a collector mesh is provided at each desk, at -X volts, but shielded so that you can't touch it and shock yourself. What X is large enough to ensure that all the virus particles you cough out end up at the collector? Is it possible to do this without electrocuting everyone?

This seems to assume that virus particles are charged. If they are neutral, they wouldn't be driven in any direction by an electric field. Am I missing something? Is it known that virus particles have a charge?

Re: The experiment that proved airborne disease transmission

#56

Post by fyfy18 »

dangrossman wrote: post #33
lifeisstillgood wrote: post #23

UV-C lights that irradiate an air duct is literally the most surprising (and in retrospect obvious) thing I learnt today. Is this something a household HVAC could be upgraded to. Do HNers in areas that have air con think it's a "yeah people will want that" idea?

Any HVAC company can install this for you right now, or you can buy a kit and do it yourself. A UV light bulb to install in your central air system is an off the shelf product. "Whole house UV air purifier" as a search term will pull these up.

Are these products actually effective though? I mean the duration and intensity required to kill viruses in moving air must be quite high? Or is it just snake oil, like how a lot of hand dryers have bluish/purple LEDs (which emit no UV) that shine on your hands?

Re: The experiment that proved airborne disease transmission

#58

Post by jakear »

throwmeaway_pls wrote: post #46
endgame wrote: post #40

Earlier quoted context omitted.

Not the first time we were lied to as part of this disaster: https://www.nytimes.com/2020/09/30/world/europe/ski-party-pa... Turns out the "don't close borders" advice was a cached thought related to a plague outbreak in India over 25 years ago, and welded in place by politics.

This culture of deceit needs to change. I don’t blame anybody for not following the rules.

Agreed. US official response has been to lie to the population so as to “not cause a panic” then act shocked when that same population doesn’t trust the officials anymore. Go figure.

Re: The experiment that proved airborne disease transmission

#59

Post by tzs »

TheSpiceIsLife wrote: post #24
lifeisstillgood wrote: post #23

UV-C lights that irradiate an air duct is literally the most surprising (and in retrospect obvious) thing I learnt today. Is this something a household HVAC could be upgraded to. Do HNers in areas that have air con think it's a "yeah people will want that" idea?

What magnitude of irradiance is required? If the required power is,say, 500w continues, or more, that's going to get quite expensive to run. For example, where I live running a 500w device 24/7 is going to add an extra $1100 a year to the power bill.

Looking at germicidal bulbs at 1000bulbs.com, the highest wattage bulb they have is 65 watts [1]. Most are well under that.

Looking at random in-duct systems, it looks like they range from 1 to 10 or so bulbs with the later being for commercial buildings. Home systems seem to lean toward 1 or 2 bulbs of maybe 20ish watts or so total. This site [2] says typically $15-30 per year energy cost

[1] https://www.1000bulbs.com/product/113917/AU-LG64T5L.html

[2] https://www.pickhvac.com/faq/hvac-uv-lights/

Re: The experiment that proved airborne disease transmission

#60

Post by endogui »

Zenst wrote: post #9
redis_mlc wrote: post #2

[flagged]

I was thinking HEPA filtration may already cater for virus's, but with HEPA certification being .3 microns and the COVID-19 virus 0.12 microns, then it gets down to individual air conditioning systems. Some may use ionising in combination or UV. So I foresee a whole raft of legislation and requirements for office spaces ahead. Which will only help drive the work from home long-term as cheaper office space. But also h…

> Corona-viruses from my understanding, do mutate.

Already, reinfection by different strains of COVID-19 has been documented (by DNA sequencing) in Korea. The more people who catch COVID-19, the greater the space of possible genetic mutations can be explored. Some of those mutations may decrease severity, but others are likely to merely increase the presympomatic contagiousness period.

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