U.V. or not U.V., that is the question

archibald tuttle

so our one building with scorched air turns out to the first that has a tenant with nonsymptomatic positive covid test. murphy didn't do us in all the way as they are on the 3rd floor which was an afterthought to the forced air heating system and there is no return, only a few supply ducts with marginal air flow with much comfort provided simply because the floor below is heated.

But it got me thinking about what I should do prophylactically about filtration in the modern era. We went from typical double 1" filters in old furnace to 20x25x5 air bear when changing to condensing furance.

So the first thing I did was look into uping the MERV rating on our filter and trying to gauge the limit that system design would impose here with 13 being a minimum and higher being even more efficacious at E1 particle removal, the focus for particles to which viruses are likely attached in circulation from my understanding.

The highest I could find locally available from dozens of shops was a 12 and those guys were outliers. All others had only 10s or 11s.

Trion themselves only offers a 13 which I mail ordered with an aftermarket 14. I'm going to test the pressure differentials in the plenums before and after as well as plenum temperature. IIRC I've got the multispeed fan runs on medium most of the time and i disabled low because the plenum temps were too high. So I might have to run the fun locked on high. Small price to pay, as it were and judge between the circulatory performance vs. filtering efficaciousness of the 13 vs. the 14.

In any event, in this environment can't help but think of alternatives. maybe it is the high pressure drops that lead suppliers not to stock the higher MERV rated filters almost a year into the sudden focus on interior air quality, and/or maybe the focus is on small commercial spaces and not residential. As far as alternatives, I was thinking UV at first. But other than directly focused on the evaporator to limit mold i'm wondering if there really is an additional 'filtering' or air wash approach that I could implement in either supply or return plenum. And I do notice the honeywell F300 electrostatic with pre and post filter is supposed to give MERV 14ish performance with an airbear sized footprint and mostly reuseable/washable media as a kind of swap out.

Most of the feedback you can get on these active filtering/treatment approaches speaks to their effectiveness against mold (which has not been a problem in this building at all) but I'm pondering if mold is a good surrogate for viruses in terms of reasonable best practices at the present moment and asking what theoretical or empirical knowledge all you steam and hydronic heads have in this realm.

thanks,

brian

pecmsg

Before changing or installing a High MERV filter have the static or TESP for the furnace tested. Air Bear is probably all that's needed.

EdTheHeaterMan

I was always of the understanding that the Honeywell EAC was effective on particle removal down to the size of viruses. May not be 100% of all viruses, but the multiple passes thru the filters will remove them over time.  You know law of diminishing returns and all.   So you get maybe half of them on the first go round and half of the remaining on the second go round and so on.  

I was a big fan of EAC technology when I was selling scorched air systems in the 1990s

Yours truly,
Mr. Ed

PS I like the title on this discussion 

WMno57

The knowledge on COVID is incomplete and evolving. We know some things as fact. We have some theories. There are still unknowns.

"Each SARS-CoV-2 virion is 50–200 nanometres in diameter."
https://en.wikipedia.org/wiki/Severe_acute_respiratory_syndrome_coronavirus_2#Structural_biology

We know the flu virus is more of a problem in winter because low temperature and low humidity help it remain viable outside a host for longer. The flu virus has a protective shell that becomes harder when it dries out (low humidity of cold dry winter air). Higher temperature and humidity eventually kill virions outside a host.

"Out of a host, flu viruses can remain infectious for about one week at human body temperature, over 30 days at 0 °C (32 °F), and indefinitely at very low temperatures"
https://en.wikipedia.org/wiki/Orthomyxoviridae#Replication_cycle

I suspect traveling through the heat exchanger will kill most of the virions. You have to get through this winter. Hopefully next winter COVID will be under control.

Could you raise the thermostat a couple degrees and add a humidifier? That might be the most cost effective solution.

Jamie Hall

Two things to remember here. First, what we are dealing with is a virus, not a bacterium, and they are much harder to deactivate (you don't kill virus). Second, the virus itself is small enough that even full HEPA filtration is only marginally adequate, unless one is concerned with particles to which the virus is attached.

To look at the title of the thread, though, UV will deactivate virus, including this nasty -- but it must be at an intensity which must be shielded. I believe, though I haven't looked it up, that units are available for forced air systems.

ChrisJ

The only thing I can add to what jamie said is my mediocre understanding of what a virus is.  I'm not in the medical field at all, so this is merely what I've come up with reading forums etc.

Most do not consider a virus to be living (some do, it seems to cause big arguments).  Its simply a set of instructions, much like an owners manual.  It cannot do anything on it own.  So like jamie said you wouldn't be killing it, but rather destroying the information.  Like leaving a thermal paper receipt in the sun too long.

I also think when a virus mutates, its just mistakes in the reproduction in it, sometimes beneficial and sometimes harmful.  

But like I said this is far from my area of expertise.  I would recommend doing your own research.


I'm not sure how a UV light would do. I had heard the typical residential ones didn't do much and I think things need to (see the light) directly for a minimal amount of time vs the brightness.

What do hospitals use?

neilc

I tested positive a week after holloween,
the week prior I had added a GPS Ion device to my home furnace(little did I know),
I had the "flu" for about a week,
wife and I sat at opposite ends of a 6 ft couch, with masks, for tv, dinner, etc.
far as we know, she never got it,

where I work they were also installed in every AHU, RTU, and mitsu heat pumps, etc,
we've had no outbreak at this full occupancy, private school, non boarding,
they also added several tents with sides and heat for added socailly distant occupancy space.

https://globalplasmasolutions.com/how-it-works

Jamie Hall

Home UV lights simply don't do anything to it to speak of. Industrial/medical UV disinfecting lights do -- but as I said, those have to be shielded from sight when operating, as they also cause pretty much immediate skin and eye damage.

On getting it or not. There seems to be an idea that if you are in close social contact with someone who has it you will also get it. The media just love that idea, along with OMG we'll all die. Simply not true. The case cited by @neilc is not at all unusual -- with or without all the bells and whistles. It is true that it seems to be more contagious than some other respiratory viral diseases, and it is also true that some people who get it will become very sick, and some will die. On the other hand, it is also true that even among those who can be shown to have it, a substantial fraction show no symptoms to speak of at all.

ChrisJ

@Jamie Hall since you brought it up, it's also been shown a high percentage of people that get it and even those who show no symptoms also have lung and or heart damage and they don't know if it's permanent or not.  


Let's not forget the effects strep can have on your heart if left untreated and it doesn't usually show up for a long time. 

Jamie Hall

Oh I quite agree. You don't want to get Covid. You also don't want to get a lot of other things. There are a lot of things you can eat which will hasten your demise. There are sports which are a bit chancy.

I firmly advocate taking all reasonable precautions -- for Covid or anything else. I also advocate living while you are alive -- and accepting that you won't be forever.

Zman

UV has been around forever. It certainly will help with Covid but I wonder how many business will commit to the expensive upkeep UV requires.

The high merves will also help, assuming you have enough fan and you don't reduce your flow rates. You will have to change the filters a lot more often with high merves. Again it will take a commitment from the owner to keep up with filter changes.

The GPS technology that @neilc mentioned is all the rage in my local HVAC world. The theory sounds great and everyone is jumping on board. I have yet to see a scientific study that proves it works. I sure hope it does...

neilc

gps has white papers saying so,
fake news though, right?
makes little viruses sticky, to each other, and bigger things, or the floor, easier to filter

I had forgot to include,
also upgraded filtration from where it was 8, to 13,
I was absent minded precovid also,

get humidity to between 40 and 60 RH,
this we have not done

Jamie Hall

It really all depends on what you are trying to kill or deactivate. Bacteria, protozoans, amoeba, molds -- piece of cake. Relatively speaking, they're fragile. There are any number of disinfectants which work well, and they are big enough so that filtration can achieve very high removal rates. Virus are another story. They're amazingly tough -- and very small. If they are riding on particles, then filtration works nicely -- including fancy things like ionization and clumping. If they are free floating... problem. You either have to oxidize them (such as high levels of chlorine or other halogens, or, even better, ozone or hydrogen peroxide) or disrupt them with radiation, which is what UV does. Both approaches require adequate mixing and contact time.

It's not air, but I once designed a wastewater treatment facility for a hospital. Our objective was five nines removal for anything except virus, and four nines for virus. I wound up with a combination of slow sand filtration, followed by ozonation, followed by UV radiation. Not cheap, but it worked.

Zman

neilc said:

gps has white papers saying so,
fake news though, right?
makes little viruses sticky, to each other, and bigger things, or the floor, easier to filter

I had forgot to include,
also upgraded filtration from where it was 8, to 13,
I was absent minded precovid also,

get humidity to between 40 and 60 RH,
this we have not done

I have not seen a white paper on the GPS that proves anything. I read one where they claimed ~98% success after 30 minutes, it sounded great but there was no control showing the rate without GPS.

Please post what you have read. I am genuinely interested. I am more of a "real science" kind of person.

WMno57

Zman said:

Please post what you have read. I am genuinely interested. I am more of a "real science" kind of person.

Got a half hour to waste?

https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation.html#refphf

scroll down and expand the FAQs at the bottom of the page.

It's a rabbit hole of scientific blah blah blah.

ChrisJ

WMno57 said:

Please post what you have read. I am genuinely interested. I am more of a "real science" kind of person.

Got a half hour to waste? https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation.html#refphf scroll down and expand the FAQs at the bottom of the page. It's a rabbit hole of scientific blah blah blah.

What exactly is "scientific blah blah blah"?

archibald tuttle

wow, my spam filter must be reacting to the wall, cause i didn't see an email that this had generated comments. glad i got my sunday morning coffee pulled up next to the computer and perambulated around to the places i was yesterday.

If I'm reading this correctly:

@zman higher MERV can't hurt if it doesn't create insufficient airflow, but filters require more frequent change ( I assume because the higher capture efficiency would create insufficient airflow more quickly even if the clean filter itself does not)

@Jamie Hall higher MERV still only significantly effective against particles to which viruses are attached, not against 'free' or 'free floating' virus. (so whats the relative prevalance of the former and latter in typical scorched air home?)

@neilc GPS(globalplasmasolutions) addresses the problem of free vs attached virus (virons?)

@zman 'show me the beef'

at CDC 'caveat emptor'

at GPS 'independent lab says yes'–don't know if i should have put scare quotes around 'independent' given its self promotional literature. assuming the data is real some reduction in pathogens although one principal field test documented reduction at the low end of the E1 scale (.3 microns, i.e. 300 'nanons'–my syllable saving convenience for nanometers) at 87% but the virus itself is 60 to 140 nanons in size so impact is dependent on attachment to larger particles which the literature claims it fosters, but that is maybe only documented indirectly as reduction in surface pathogens in test rooms compared to control rooms. I'm prepared to consider that useful info if it is replicated.

@Jamie Hall 'UV maybe'. the thing that startles me with UV compared to the electostatic honeywell I linked is that someone familiar with the industry recognizes the honeywell as a component that they can readily install in existing system, i.e. it looks like an air bear(or maybe an air bear looks like it, don't know which was first to the party). Both the GPS ionizer (I think the difference between the GPS and honeywell is the honeywell is designed to use ionization to precipitate vs. the idea of circulating ionized air which according to their theory creates larger particles through the ionic attraction that are then captured by the standard filter) and UV systems aren't presented in a form I recognize as to where they are attached and how their effect is brought to bear across the entire moving column of air in the return or supply plenum. I have never had to deal with a mold problem but it seems that, before interest in covid particles, the most common application for UV was to be positioned above the evaporator bathing it in UV during air conditioning season to limit growth catalyzed by airborne mold and moisture on the evaporator. So if you had or installed such a system would that help with virus particles? And what do these systems actually look like, bar or tubes installed above the evaporator in the plenum or floodlight style UV installed in a hole in the side of the plenum?

@WMno57 higher plenum temps could help (instinct or interpolation from flu replication where the higher the temp the shorter the persistance of flu virus as infectious?) (and guess that's thumbs up for higher MERV effects as long as its within max acceptable range and can keep up with most design temps insofar as CFM) try a humidifier with higher temps as dryer air aids persistance.

@pecmsg ck static pressure before upping the MERV. (@Erin Holohan Haskell how come there is no thumbs up in the smileys?)

@Jamie Hall 'don't worry be happy' (@Erin Holohan Haskell how come there is no smiley with tears of laughter.) or maybe 'do worry don't obsess'

thanks for all the comments

Jamie Hall

I have no idea what the prevalence of free floating vs. adhered virus is in air, @archibald tuttle ! Not the slightest.

Both the Honeywell and the GPS system appear to be attempting to do the same thing -- use ionization to cause airborne particles to stick to each other and ether become easier to filter or to precipitate. There are other systems which also use electrostatics similarly, plus creating a charge on the particles and hopefully get them to stick to oppositely charged grids. I dare say they all work -- certainly electrostatic precipitators do. For particulates.

And I'd prefer "do worry, don't obsess". Not a bad approach.

neilc

Zman said:

neilc said:

gps has white papers saying so,
fake news though, right?
makes little viruses sticky, to each other, and bigger things, or the floor, easier to filter

I had forgot to include,
also upgraded filtration from where it was 8, to 13,
I was absent minded precovid also,

get humidity to between 40 and 60 RH,
this we have not done

I have not seen a white paper on the GPS that proves anything. I read one where they claimed ~98% success after 30 minutes, it sounded great but there was no control showing the rate without GPS.

Please post what you have read. I am genuinely interested. I am more of a "real science" kind of person.

Zman and all,
I was referring to the(a) white paper at the GPS website,
and without going back to read it again, I agree with your bolded statement above,
that, and it being on the manufacturer's own website , , ,
therefore, I added my "fake news" disclaimer,

if I remember correctly, ashrea has added ionization technologies to their covid pages as "possibilities",
where ionization was not listed 10 months ago when this all broke.

neilc

ChrisJ said:

WMno57 said:

Zman said:

Please post what you have read. I am genuinely interested. I am more of a "real science" kind of person.

Got a half hour to waste?

https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation.html#refphf

scroll down and expand the FAQs at the bottom of the page.

It's a rabbit hole of scientific blah blah blah.

What exactly is "scientific blah blah blah"?




stuff you find at the bottom of rabbit holes

neilc

further disclaimer,
what I wrote in my first post to this thread is purely anecdotal, my experience(s)
drink the coolaide with grains of salt

Zman

neilc said:

further disclaimer,
what I wrote in my first post to this thread is purely anecdotal, my experience(s)
drink the coolaide with grains of salt

I think that the GPS probably helps and I am not saying it is "koolade". ASHRAE has allowed reduced OA for systems that have it (precovid).
My point is that many are stating as fact that it kills COVID and are offering zero proof.
I really hope that GPS is helping the fight, my mind can't buy in until I see some real data...

WMno57

"What exactly is "scientific blah blah blah"?

Were you ever assigned a 5000 word paper where you could succinctly describe the topic in 1000 words? You may have heard the term novel coronavirus. Novel = New. New means we don't know enough about it yet.

I grew up in a scientific household. My parents were microbiologists. Dad had multiple business trips to the CDC in Atlanta. We had dinner table conversations about certain bacteria spores that are harder to kill than virions. We even talked about prions which are harder to kill than virions. I know the difference between kill and deactivate. I'm using the word "kill" to be succinct.

Save your money on the UV stuff.
Open the windows (the dead men were right).
Drink milk and sun bathe (but not too much). If you are lactose intolerant, find another way to get vitamin D. Your immune system needs vitamin D.

The groups being hit hardest by COVID are pigmentally blessed (less vitamin D from the sun) and/or lactose intolerant. This is not meant to be dismissive of socioeconomic factors which also cause more deaths.

If you're milk drink'in pigmentally challenged like me, you still need to wear a mask and get the vaccine. Also, see a dermatologist annually. Skin cancer sucks.