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SpaceNut

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From: New Hampshire

Registered: 2004-07-22

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Virus filtration killing systems

Have split out the topic as it is about the equipment and needs for it to work...from the corona virus topic

UV lights can be gotten for room use, Circulating air that is filtered and treated is also not a large expense for UV put in place within the duct work.
The quantity versus time for class room can be lowered by changing how many are allowed into a room that has limits even when doing all of the above. Maybe its time to look at schools as a shift of hours for a given quantity of students as well. Some would do better in some cases as we have night owls and early rises...

tahanson43206

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Registered: 2018-04-27

Posts: 19,391

Re: Virus filtration killing systems

For SpaceNut re #530

Thanks for the reminder of UV light as a method of killing virus bodies floating in the air.

However, thanks in particular for association of UV light as a method that might be employed in small scale air conditioning systems, such as those for homes and small businesses and even cars or buses, as well as large scale enterprises such as hotels, condominiums and government buildings.

In order for this idea to be practical, the method would need to be effective and affordable.

What I would be interested in knowing, if I were in a position to fund development of products along these lines, is how much time a virus (Covid-19 or any other) needs to spend in what level of UV light before it becomes disabled.  That information would then lead to engineering the design of air flow for a given customer, and to the ability to estimate the energy cost for the lighting.

The information would seem likely to be available, since there are already UV lighting systems available for purchase for mobile disinfecting of vehicles and fixed site installations.

Edit#1: It would be useful to be able to sample virus sized particles in real time, to know how well the disinfection process is working. To my knowledge the ** only ** way currently available to determine the presence of live virus is the electron microscope.  My attempts to find out about the potential of this approach have (so far) borne no fruit.  Some of those attempts have been reported elsewhere in the forum.

(th)

Last edited by tahanson43206 (2020-07-18 10:48:24)

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Virus filtration killing systems

Coronavirus Sparks New Interest In Using Ultraviolet Light To Disinfect Indoor Air

Research already shows that germicidal UV can effectively inactivate airborne microbes that transmit measles, tuberculosis and SARS-CoV-1, a close relative of the novel coronavirus.

Research shows close to 90% of airborne particles from a previous coronavirus (SARS-CoV-1) can be inactivated in about 16 seconds when exposed to the same strength of UV as in the restaurant's ceiling.

How an Air Purifier Could Capture the Coronavirus

HEPA filters are very effective, certified to capture 99.97 percent of particles that are precisely 0.3 micron in diameter. The novel coronavirus itself is 0.125 microns, but Marr says the droplets it travels in—when people cough, talk, or breathe—initially are larger, around 1 micron. That's a size easily captured by HEPA filters. Consumer Reports does not test air purifiers for virus removal, but we do perform our tests using similarly sized airborne particles as small as 0.1 micron and up to 1 micron

tahanson43206

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Registered: 2018-04-27

Posts: 19,391

Re: Virus filtration killing systems

For SpaceNut re #532

Thank you for your follow up on UV filters for HVAC systems.

I would like to see a filtration system that cleans itself.  The idea of collecting all those little critters in a typical filter for a month (as a typical change time) is concerning.  The ideal (from my point of view) would be a filter that performs at the .3 micron level as your quote shows, but that revolves slowly so that as the filter winds around a drum below the action window (duct) it would receive cleansing so that when it comes back into the active window (duct) it would be clean.

Your quote of 16 seconds suggests to me that the UV light needs to be intense on a volume of air as it travels through the UV duct for a total of 16 seconds.  I'd be quite surprised if a volume of air takes more than a second to traverse the filter in a typical home HVAC system.

(th)

SpaceNut

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From: New Hampshire

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Re: Virus filtration killing systems

Another important part of the HVAC system is an ionic breeze air purifier provides trouble-free operation.

Turn the machine on, the power indicator comes on and negative ions weigh down impurities in the air, causing them to drop to the floor and leaving you with cleaner air to breathe. Occasionally, the blades require cleaning.

Where they are installed, air purifiers can help reduce the likelihood that a virus is spread. A quality air purifier will utilize effective ionization technology to proactively neutralize airborne and surface-borne viruses. Because COVID-19 is prevalent in most states, strategizing now to provide ultimate protection for your home could include buying an air purifier that uses ionization.

The most effective kind of air purifiers for viruses like COVID-19 use ionic air purification. Ionization is a process that blankets an entire room or home, addressing viruses both in the air and on surfaces.

It is a far more thorough and superior approach to home health than filtration-only systems. Filters are passive: they only treat what they trap in the filter media.

In contrast, ions neutralize airborne viruses as well as viruses on your tables, counters, furniture, etc. The ions interact with contaminants in a way that prevents them from spreading. Selecting a purifier with long-lasting ions is key.

Ionic air purifiers have a proven track record against viruses similar to COVID-19. In numerous studies, there is ample evidence that air purifiers can kill viruses.

https://www.consumerreports.org/air-pur … ronavirus/
https://info.airoasis.com/blog/ionic-ai … d-covid-19

This technology has been used in submarines for decades and works by sending air across charged plates to trap the dirt and other stuff on them. You turn power off , remove and wash them, get them dry and reinstall for the next cycle of use. The screens and filters are for the bulk filtering and are intended to be thrown out.

tahanson43206

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Registered: 2018-04-27

Posts: 19,391

Re: Virus filtration killing systems

For SpaceNut re #534

That's an interesting quote, but it was presented to the forum without your usual attention to detail.

If you have time this weekend, please go back and add the source link.

***

My concern with the claims made in the text is multifold, so I'll wait until you have a chance to add the source details before I pursue them. 

What is needed for Earth ** and ** for Mars (and any off-Earth location) is air filtration equipment that operates at the .3 micron scale, and which processes large volumes of air rapidly and continuously for years on end, allowing only oxygen, nitrogen (or other neutral gas) and such other gases as may be considered both medically acceptable and environmentally desirable.

The automated cleaning process I described earlier needs to be a part of any such system.

(th)

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Virus filtration killing systems

The motors are not that different to any brand of fan and while we need to once in a blue moon need to clean it we do so with protective gear. The micro filters are typically paper and are disposed of once we have had enough air flowing through them.

I see your rotating drum filter now and its a back wash system to clean the dirt out would be cause for concern for those in the area when it did it as you are putting the germs back into the environment that we have tried to keep clean. The particles go into the filter and must be blown out in the opposite direction.

For space we would be losing the air needed to clean them via venting the surface that is being air cleaned to space....

We are seeing this way to often Touching video shows 90-year-old man saying final goodbyes to wife with COVID-19

I believe for health consideration that entry and use rules are pretty much known and with corona mask are now just another rule. Colorado woman in viral video calls store employees asking her to wear mask 'Nazis' yet 11 Major Grocery Chains That Have Face Mask Rules

Hopefully they will all make it through this as 85 infants test positive for COVID-19 in Texas county amid alarming spike

Another place with high infection rates Florida’s DeSantis Says Virus Antibody Tests Show 16% Positive

Since the front line is so important I am wondering why I signed up to risk my life saving patients. In return, I got a pink slip.

tahanson43206

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Registered: 2018-04-27

Posts: 19,391

Re: Virus filtration killing systems

For SpaceNut re #536 and changes to #534

Thanks for adding really helpful additions to #534!

It is good to know (for me, "learn") that the systems used in submarines are designed to be easily washable.

Paper is not an optimum solution when paper cannot be supplied in inexhaustible quantities.

***
One opportunity does appear from this discussion ... there would appear to be a need for design of a moving filtration system able to completely clean whatever the filter material is as the belt passes out of the active area (ie, duct) and into the cleaning area.

It should be possible to immerse the belt in liquid designed to pull microbes and other debris out of the filters.  Clean air can then be forced through the filter to dry it before it travels back into the duct.  The cleaning of the liquid is another challenge, of course.

Thanks again for additions to the topic!

(th)

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Virus filtration killing systems

https://www.yahoo.com/news/rare-air-u-m … 00082.html

https://www.nasa.gov/mission_pages/stat … t_testbed/

https://www.nasa.gov/mission_pages/stat … dvasc.html

https://ntrs.nasa.gov/archive/nasa/casi … 008803.pdf

ISS Lab module volume is 108.6 m3 (3834 ft3).
Required ventilation flow rate is 11 m3/min (400 cfm).
ISS Bacterial Filter Elements (BFEs) are HEPA-grade filters Original replacement interval of 1 year.
Replacement interval was extended to 2-5 years.

tahanson43206

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Registered: 2018-04-27

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Re: Virus filtration killing systems

For SpaceNut re #9

Outstanding new topic!  It is relevant to RobertDyck's Large Scale passenger ship, as well as to each and every human occupied volume in any off-Earth location, as well as many locations on Earth!

The HEPA-grade filters (from your report) would (apparently) serve for RobertDyck's 2 year expedition concept, and they could be swapped out when the ship gets back to Earth.

However, I would like to call for not giving up just yet, on a continuous cleaning process design.

In a gravity field it is possible to imagine the filter descending from the duct where it has collected debris, into a liquid where that debris is absorbed into the liquid, which would then have to be cleaned in a separate process.   The filter itself would then pass through an air stream to remove any lingering particles and any lingering liquid molecules.  Finally, the filter would return to the outbound side of the duct flow, where it would pick up any particles missed by the filter material on the down flow, on the inbound side of the duct flow.

However, the problem is more complicated in the absence of gravity.

Here is an opportunity for a creative member of the active forum to contribute suggestions.

(th)

SpaceNut

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Re: Virus filtration killing systems

https://en.wikipedia.org/wiki/HEPA

HEPA filters are composed of a mat of randomly arranged fibres. The fibers are typically composed of fiberglass and possess diameters between 0.5 and 2.0 micrometers. Key factors affecting its functions are fiber diameter, filter thickness, and face velocity. The air space between HEPA filter fibers is typically much greater than 0.3 μm.

As for the solution it would contain most likely hydrogen peroxide and alcohol in water but there will be a need for safe precautions.

tahanson43206

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Re: Virus filtration killing systems

For SpaceNut re #11 ... thank you for the suggestion of a liquid mixture of hydrogen peroxide and alcohol in water.

it seems to me we are on the verge of describing an entire industry << grin >>

From my volunteer work I know about a product called "Rescue"...

hydrogen peroxide
Rescue is non-toxic and non-irritating. The only active ingredient is hydrogen peroxide, a non-toxic substance that evaporates into oxygen and water.

Frequently Asked Questions - Rescue How To

The blurb states that Rescue is non-toxic and non-irritating ... to my way of thinking, that is an advertising error.

First of all, hydrogen peroxide is most definitely toxic to microbes it envelopes.  And it is most definitely irritating to humans who apply it.

I found that in the stronger mixtures occasionally required, and in confined spaces typical of cages, it is ** extremely ** irritating, in the sense of being annoyed. 

Thus, I am picking up on your advice that there would need to be "safe precautions".

In the system (I think) we are discussing, the thoroughly cleaned filter belt would roll past a work station that would have the responsibility to remove any lingering solution entirely from the filter material, and it would have to do that quickly, although perhaps the rate of travel of the filter belt might not be high, if it is moving at a rate that captures contaminants in the return air that matches the need.

Perhaps there could be sensors (of some kind) designed into the system to detect contamination levels and adjust the speed of the filter belt accordingly.

An application of this kind of a system could be collecting combustion products in the case of any combustion that might occur in a space rated volume.  Incidents have occurred in space in the past, in which unwanted chemical reactions have delivered contaminants to the breathing air volume.

Do you have additional ideas for another round?

Other forum members are welcome to contribute!

This discussion should be of more than academic interest to any human alive on Earth, whether they are going to Mars or not.

(th)

SpaceNut

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From: New Hampshire

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Posts: 29,431

Re: Virus filtration killing systems

Ok thinking about the volume and number of inlets to outlets we can assume that the system has multiple redundancy for if a section should need to be shut down for repairs. That said a portable unit for air cleaning would be a plug in powered unit for just that purpose.

Vent inlet size has to do with cfm of air flow that's needed within any space that we are cleaning. Vent tube that connects the system means that wall thickness is the limiter for both the vent face and for the flow rates to a greater degree once we select the fan for the flow we are stuck with making it work to those specs. The only variable to play with is the fan blade rpm to gain the increase of flow.

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Virus filtration killing systems

Could a century-old technology zap coronavirus in schools and offices?