Corsi/Rosenthal Box FAQ

box fan filter FAQ

See also our main DIY box fan filter page

Build

Essential

Click here to go back to all FAQ’s.


Before reading any farther, even with 2 or 3 portable air cleaners in your space, everyone must wear a mask (more on masks, kids’ masks and reusable elastomeric respirators).

Like getting closer to a cigarette smoker, respiratory aerosols get thicker in concentration as you get closer to people. We give off respiratory aerosols when we breathe, talk, yell, laugh, and sing.

Regarding lunch and breaks – of course masks come off, so the risk goes up. Here are many ideas on how to handle those times.


Introduction

You are probably interested in the DIY Air Cleaner known as the Corsi/Rosenthal Box. Conceived by Dr. Corsi, then built by Jim Rosenthal, Chairman and Chief Executive Officer of Air Relief Technologies, Inc. and past president of the National Air Filtration Association (NAFA).

To be crystal clear about appearances of Conflict of Interest, this website is put together by Citizen Scientists who have been learning about Indoor Air Quality (IAQ) from the multitude of IAQ experts, engineers, and scientists on Twitter, amongst other places.

While Dr. Corsi and Jim Rosenthal are referred to, and cited frequently, that same information has been either vetted by other IAQ experts or obtained from them separately.


Sections

These FAQ’s are divided into sections.

  • Build – everything necessary just to get building.
  • “Not sure” – the FAQ’s that dive into why reducing the amount of SARS-COV-2 laden aerosols are important. And whether or not portable air cleaners do that – especially the Corsi/Rosenthal Box.
  • Implementation – important details on how to use – like where to place it in the room.
  • Safety – addresses safety concerns of all sorts.
  • General Questions – addresses most everything not in the above categores.
  • Countries – not all countries have the same materials as in the US.
Did you find this FAQ helpful?
11
0

Click here to go back to all FAQ’s.

End goal:

Shopping List – the below links may quickly no longer be valid, so including a description of each item.  No affiliation with any company whose products I have listed:

Build time!

Tape the boxes together- very important to point the arrows on the edges of the filters, inwards.

Tape the fan to the front, windy-side out.

Make sure there aren’t any seams where air can get through. The idea is that the fan pulls the air through the filters.


Next, we are going to make a fan shroud. Directions here.

With the shroud done, you need some clearance under it. See below…see how the box is off of the ground?

“These are 20” strips cut from “pallet” protectors. But any reasonably sturdy material will work. The completed box is very light.”

So, try folding some cardboard in 1/2 to make a triangle, or cut a 1″x1″ board to fit.

The clearance is great below this build – though it would be best to have the fan on top pointing up.  With the fan pointing down, there’s more of a chance of dried respiratory aerosols being blown back up into the air.

This build is terrific because it’s build on casters!!!!  With school colors for the tape!

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
2
0

Click here to go back to all FAQ’s.

There are several different builds below. No matter which one you choose make sure you put a shroud on the front of the fan to enhance efficiency.

Here is a 4 filter build known as the Compretto Cube: hosted by Philip Neustrom.  This diagram is just a sample – very well-done build site!

Here’s another 4 filter build from Don Blair, citizen scientist in the Boston area.  Great Work Don!  Great NPR article on this.

PNG of this poster.

Very handy PDF download here.

Here’s a video on how to do it from This Old House:

Here’s another video build:

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
4
0

Click here to go back to all FAQ’s.

Here’s one as a goal – it’s the same triangle filter as in the video, but with a shroud added for optimum performance, and adhesive contact liner layered over the cardboard.  Beautifully done!

This was what it looked like before the contact paper was added.

In this one, you’ll notice that the shroud ismade of tape.

Immediately below is the build thread ( make sure you put a shroud on the front of the fan to enhance efficiency):

 

Slightly different build.

Here’s a slightly different build. I like this one for the step by step instructions (make sure you put a shroud on the front of the fan to enhance efficiency):

Video Build

Here’s an alternate build video (make sure you put a shroud on the front of the fan to enhance efficiency):

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.

The single filter version did very well vs commercial air cleaners.

 

Here’s what the final build can look like with judicious use of duct tape. Pretty, pretty sharp:

Here are the actual measurements:

Actual Build

 Here’s the actual build from the above Twitter thread. 

Here’s a more simple, slightly less effective single filter build by aerosol scientist, Dr. Huffman.

And here’s a single filter build, but with a 4″ filter.  It should be very close to the 4 filter Corsi/Rosenthal Box in performance.

No matter which build you do – make sure you put a shroud on the front of the fan to enhance efficiency.

With the single filter build, if you have 3 of them – you are going to have great results:

 

One last option shown below

 Won’t be as good – but something is better than nothing!

You could make that something even better by replacing the MERV 10 filter it comes with, with a MERV 13-A filter.

 

Click here to go back to all FAQ’s.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

Some countries don’t have box fans, but have round fans.

“Presenting V1.0 accessible, effective and validated DIY filters using round fans inspired by the #CorsiRosenthalBox. They are the result of international collaboration from designers, engineers and advocates in @TheWHN Airborne Group DIY Filter Team.”. Source here.

For the type of fan, “For gym fans, anything between 80-120w 16-18″ is best. Aim lower for quietest operation. These designs and numbers were tested using a 18″ 45 cm gym cage fan. Best not to go above 120w. Will likely be running setting 1 or 2. Highest power flow is large but unstable & noisy.”. Source.

“Calculated based on 62% filter efficiency but we have particle measurements for Aerostar brand. We’re building and testing in UK,Spain,Canada,Switzerland. “. Source.

“Using ISO 5801 pressure balanced calibrated flow test. Similar to described in this paper .” Source.

4 Filter Build

1 Filter Build

1 Filter Build Video

2 Filter Build (Wedge Shape)

Some creative ideas:

4/ 5 Filter Build

A most excellent idea is this one, by ChurchAndCoVid : “The plywood (OSB) is 21”x21” (53 cm). Fan diameter is ~16” (40 cm) This could go on top of 4 merv-13 filters or a frame with polypropylene sheet.”

This is from here – an excellent build site hosted by Philip Neustrom.

A round fan that might work with a box combination:

 

A round fan video build below, found by David Elfstrom:

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Translations by Emily Barnes Franklin – thank you!

Click here to go back to all FAQ’s.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

Please see our air cleaner/filter buying guide.

Also these tweets are two excellent sources – both from Indoor Air Quality Experts.

This is Dr. Shelly Miller – who authored this tweet – and co-authored the tools she mentions here.


This is Marwa Zaatari, who regularly helps decipher the complex air cleaner market to get you the best bang for your buck.


Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.

“Lasko FF305 Air Flex 2-in-1 20-inch Box Fan and Air Purifier in One with MERV10 Air Purifying Filter”

Won’t be as good – but something is better than nothing!

The filters here  are 13-A – so I would buy one and swap out the MERV 10 that it comes with.

 No affiliation, just these are hard to find.

Corsi/Rosenthal Thread Update:

Some folks, (mostly teachers) cannot bring in an air cleaner. But can bring in a fan.

Here’s a fan that has a filter built into it! So, a stealth air cleaner.

“Lasko FF305 Air Flex 2-in-1 20-inch Box Fan and Air Purifier in One with MERV10 pic.twitter.com/qPE7Yn6SWP — Lazarus Long (@LazarusLong13) August 16, 2021

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

Quick Tip if your windows and doors open – at the VERY LEAST, open during breaks and lunches. Source:

 
 

Professor Cathy Noakes:

“If its cold, crack the windows rather than opening them fully and then open them wider to air the room periodically say at break times. The colder it is, the smaller the gap you need for ventilation. And let them layer up too.

Ventilation is driven by pressure differences and they are created by temperature differences (hot air rises) and wind. So for the same size gap you get more flow when there is a bigger temp difference between indoor and outdoor or there’s a higher wind speed.

So a fairly small gap in winter can give you as much ventilation as fully open window in summer. It is hardest to ventilate when its a warm still summer day with no difference in temperature and no wind.”

Some recommended ways to help with natural ventilation from the CIBSE Natural Ventilation Chair.

Original Source is here – 41 pages of great information. But if you have no time, here’s the most relevant 4 pages to you or me, the common person. Some samples below:

Openable windows and vents should be used more than normal, as long as security is
considered and the open windows do not cause a hazard to anyone moving outside. If
possible windows should be open at least 15 minutes prior to room occupation.


“In cooler weather even a small opening can deliver significant ventilation flows, and this can minimise risk to occupants of the space.”

“Where there are both high-level and low-level openable windows in a room, it is
recommended to open the high-level windows during cooler weather
in the first instance; incoming air will be warmed as it flows down into the room, thereby reducing cold draughts.”

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.


Next, we are going to make a fan shroud..a fancy way of saying we are going to block off the square corners, so just the round fan is exposed.  This was discussed here by Jim Rosenthal.

Short version – the round fan does not reach the square corners, so there’s a gap there, and is not efficient. David Elfstrom, “At the tips of the fan blades there is negative pressure which sucks air in through the front (outlet) of the fan. By covering up this area, more air will flow through the filter on the inlet side and noise is reduced.”

As you can see below, the green arrows are where the air is flowing out of the fan, and the red arrows are where the negative pressure is sucking air back in the opposite way. Picture from here.

When you make the shroud, you will be putting it on the outside of the fan. On the side that the air is blowing from. And you only need one shroud, not one on the inside AND the outside. Just the outside.

You could do this with tape:

Or cardboard.

So – there have been two fans that have had their fans optimized by David Elfstrom. They are here. After this, will show you how to find the shroud size for your specific fan.

 

All others, you could can use tissue paper to determine how big the hole in the middle should be. As the fan is on, pull a piece of tissue across the front of the fan, slowly. You will very quickly see the part of the tissue that is being sucked back INTO the fan. You’ll want to cover that part with the shroud. In the picture below, you’ll see the green arrows up, and red arrows down – the red arrow down is the part you want to cover.

After determining the size, draw a circle on your cardboard. If you draw an “X”, corner to corner, that will give you the middle. Then, you can use this technique with a pin and string to draw that circle.

Some people put contact paper over their cardboard parts – like the shroud.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.

The Corsi/Rosenthal Box is based on a 20″ x 20″ box fan.  This is because the size perfectly matches with 20″x20″ filters.

Some countries have no box fans. Round fans have been used to build the Corsi/Rosenthal Box.

  • 20″ Box Fan – very important that the On button/ Speed Control is on the outer edges of the fan – or on the front where air comes out.  You do not want it on the back where air comes in. 
    • Lasko 20″ Box 3-Speed Fan
    • Utilitech 20-in 3-Speed Indoor Box  Fan  – these  also  come  in  black.

Safety note: the box fans have been tested and found to more than up to the task.  With that said, as an additional note, it might be good to get one with a fused plug, which the Lasko and Utilitech fans have for sure.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
3
0

Click here to go back to all FAQ’s.

Any type of duct tape is recommended. Keep in mind that you can use the duct tape color to accessorize your DIY Air Cleaner. Please see the Gallery for lots of creative fun ideas.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

20″x20″x1″ or 20″x20″x2″ MERV 13 filters are recommended. MERV 13-A filters are available here.  Why 13-A? Because they are top of the line.

If MERV 13-A filters are not available, the next filters recommended are MERV 13 filters from 3M .  Specifically, 3M 1900 filters are excellent (the people on the thread are IAQ experts) .

These can gotten at:

  • Lowe’s
  • Home Depot
  • Walmart
  • Ace Hardware
  • etc.

What is not recommended?

FilterBuy’s filters sourced from Amazon. There have been knock-offs sold on Amazon, and so it is recommended to avoid those.

Last tip – if you are making the 4 or 5 filter box, you could make the sides out of 20″x30“x1 filters – and get a huge gain in filter area. You can find 20″x30” filters at Walmart. Tip courtesy of ocnj of Twitter.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
5
0

Click here to go back to all FAQ’s.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
2
0

Click here to go back to all FAQ’s.

That study did not include the risk of reaersolization (blow back up in the air)  of dried respiratory aerosols that will have settled on the ground.   You will give a little in efficiency to gain safety.

http://poppendieck.com/IAQ/COVID19%20FAQ.html

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
5
4

This build by Amanda H, has a printed out record label in the middle.

 
 

File is located:

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
2
0

Click here to go back to all FAQ’s.

These are pictures of each tweet of someone who has built a CR Box, and all are linked to the actual tweet. This is by design so that you can click on the tweet, and ask any questions you might have directly of them. Such as, “What is the name of that contact paper?”

This first CR Box is very, very well done. It has the shroud, which with the Utilitech fan will result in a 47% improvement of performance. If the fan is a Lasko fan, it would be a 38% performance increase.

It is on casters for ease of movement, and is the 5 filter version, which is why it needs to be raised. The bottom is a filter as well. Bravo!

This next fan is the actual Tweet so that you can click on it and play.

It’s the 4 filter version, so the bottom is not a filter, but it is absolutely brilliantly done, looking like a record player.
The middle of the “record” is actually a downloadable picture.

 


Next up, we have a fantastic 5 filter CR Box with a Utilitech Fan, raised slightly to allow the air to come in the bottom. Great usage of colored duct tape – the possibilities are endless!


You’ll notice his filters are from Tex-Air Filters, which is owned by Jim Rosenthal – the R part of the Corsi-Rosenthal Box. Thanks to Jim’s industry knowledge, he was able to build Dr. Corsi’s concept, and he also innovated the usage of the shroud.


This next CR Box is a very nicely done 3 Filter build. It was one of the first to use contact paper over the cardboard, and is just tres chic.


This next one is an excellent example of the 5 Filter build. And the spacing below it is to really maximize the amount of air flow. Well done!

It should be noted that the fan optimally would be flipped the opposite way, pointing to the ceiling. This accomplices 2 things. First, it is a safety feature. It’s entirely possible that infectious respiratory aerosols have been dried out and drifted to the floor. If the fan aimed down, it could lift them back up.

Secondly, by pointing up, you are helping the air move around more efficiently. Dr. Poppendieck talks about this here.



This next 4 Filter build has a very cool use of clear packing tape, not often seen.

And brings up a topic – be very careful buying filters from Amazon. FilterBuy, these filters, had some of their filters knocked-off and sold on Amazon. Always check with an authentic distributor.

Your health is no place to decide to save a couple of bucks.



This very nicely done fan is set up in a classroom. It’s also an interesting one, where the shroud is set in the bottom of the fan, instead of the top. For optimal performance, putting the shroud on top is recommended.

Also – if you have a standard classroom, at least 2 CR Boxes are recommended – especially in a windowless room.

Beautifully done, and very nice use of white duct tape!


Amazing creativity! Class Mascot? Should be the Pandemic Mascot!

 

ThIs one shows off the creativity and fun the whole family can have. “Sharky McSharkerson”!


This next filter is a 1 Filter build, using the box that the fan came in a as an offset.

Per David Elfstrom
, this is a “1” filter with box offset to maximize exposed filter area instead of having it flat against the fan housing and corners”

Very slick use of the duct tape to give it a great, almost commercial appearance!


Here is a great little sideways-aimed 4 Filter Build. It would be better aimed up at the ceiling, but having a sideways-aimed CR Box is way better than having no CR Box!

The staging here with the books is just brilliant!


Great use of duct tape to make the shrouds below!

You might think this is a double-decker CR Box. It is not, just staged on top of each other.

And that brings up a great point. Usually, it’s better to have a couple of CR Boxes
spread around a room.


This next CR Box is a classic 4 Filter Build with duct tape shroud. It’s an example of fun for the whole family! Kids really get into building these!!

And if you are a teacher, you might think – hey – Science Project! And we got you!



Fantastic usage of 2 CR Boxes in her classroom (and really good placement) – and a great DO NOT TOUCH sign.

Should you be worried about kids touching these? Not really – and here’s why.




Talk about a clean looking CR Box! Good looking!


This box is demonstrating great spacing from walls. Sometimes you have to put them right next to walls for safety reasons, but spaced away is better!


This next box has a very chill masculine vibe. Guys have lungs, too!



This next CR Box – wow! The staging!

Using 20X25X 1 filters (often HomeDepot and Lowes have MERV13 1900 20X25X1’s at almost the same price as the smaller 20X20X1 filters)!

More bang for your buck!

I highly recommend you click on the pic – complete documentation of performance specs!


Dr. Corsi, shown below in the red nose. (IN THE LEFT PICTURE). Is famous for bringing red clown noses.



This next build is great because it shows the journey to clean lungs.


Fantastic use of colors, and such a great family project!!!


Huge projects like these ARE possible!!!!
If you need help persuading your principal or superintendent to go forward with this, we’ve got a letter prepared for you!


Perfection in one picture – that’s what this is!


Chic, cheeky, and Corsi/Rosenthal Boxes. Say goodbye to CoVid – (remember those masks!)


Great collection of 3 and 4 filter boxes! And – make sure you tag David if you do big groups of them!


Love to see the giving spirit!! There’s a newspaper article there – click away!

Great use of the box it came in to form the bottom!


Showing the shaka – right back at you, sir! Love the spirit, the 5 Filter Build – and innovative handle to move it around! Mahalo!


A CR Box is also handy for when you cook bacon! Very practical! Think about the summer with fire season!

 


Beautiful blue and yellow CR Boxes all ready to go! 18 of them. About $1800 in cost. But delivering about $16,200 in clean air. Priceless!



Incredibly beautiful box. Inspirational to tell the truth!

Don’t forget – we have a letter AND tactics to help you in your quest to protect your loved ones’ lungs!


A rare international build from Switzerland. These are the filters you want if in Switzerland!


One CR Box above, there was an inspirational box. This one is inspirational for the location. Every church needs air cleaners!!!


People have been asking if this will help a windowless classroom? YES! If you have no opening windows, then you especially need these!

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Not sure? These are the FAQ’s for you.

Click here to go back to all FAQ’s.

SARS-COV-2, the virus that causes CoVid, is actually carried by respiratory aerosols. Portable air cleaners (also called air purifiers and air filters), work by pulling air through high-quality filters.

As the air cleaner pulls air in with the fan contained in it, the filters attached to it clean the air. Details on how the filters work below*.

Respiratory aerosols (emitted when we breathe, talk, laugh, yell, sing, cough, sneeze) carry SARS-COV-2 and are extremely small. The ones most likely to carry SARS-COV-2 are too small to see.

Roughly 85% of respiratory aerosols are 5 microns or smaller. High-level tweetorial about this study.

Just to give you an idea of how small, here are 50 micron aerosols floating:


*How the filters actually clean the air.  The first thing to know is that while the filter appears to be flat, it is actually a 3 dimensional matrix of interwoven fibers.

Those fibers work via the following mechanisms:

  • Inertial impaction – Occurs when a particle encounters a filter fiber due to the inertia of the particle.
    • Example: A large dust particle is unable to change direction of flow due to its inertia, so it impacts the fiber and becomes attached to it.
  • Interception – Occurs when a particle follows a the air flow happens to come in contact with the surface of a fiber.
    • Example: An intermediate dust particle that readily follows the airflow stream comes in contact with a filter fiber.
  • Diffusion – Occurs when particles do not follow the airflows as readily and are governed by random particle motion (Brownian motion of small particles).
    • Example: A small particle, such as certain exhaust particles, encounter filter fibers at random.
  • Electrostatic attraction – Occurs when an electrostatic charge on the filter fibers are present.
    • Example: Static charge on a fabric creating static cling.

In terms of filtration, the most important filtration mechanics pertaining to everyday use are: Intertial impaction and Interception.

The larger particles that encounter the filter tend to impact onto the exterior surface of the filter.

The smaller particles that follow airflow streamlines tend to impact and intercept within the depth of the filter.

Here’s a video from the NYTimes showing how the N95 masks catch viruses.  These are the same as how air filters work.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

Sure, they are.  They have to be to enable you to breathe.  But – if you catch CoVid, you literally drown in the mucus created in your lungs.

Speaking of drowning – your lungs process over 2,000 gallons of air, per day.  That’s a swimming pool of air.  

How many respiratory aerosols could be in that?

Very rough math (sorry)…if a respiratory aerosol is 5 microns, that would be 1.51416e+18 aerosols processed.  1,514,160,000,000,000,000.

Potentially, 1.5 quintillion 5 micron aerosols.  

Your lungs handle all of that. How big are they? One of the largest organs in your body.  Not as big as your skin which can be cleaned with hand sanitizer, but close.  About the size of a tennis court if laid out flat.

Your lungs have 1,500 MILES of airways in them – imagine driving from Chicago to Las Vegas.  Now – think….if even as little as 1 SARS-COV-2 virion landed on that roadway, you could get CoVid. 

The true amount of inoculum (amount required to get you infected) is unknown, but – you get our point. 

You use those lungs to breathe 14 times per minute – over 17,000 breaths per day.  And with Delta?  Only takes one breath.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.

Because they have been studied, and found to be very effective at removing aerosols from the air: 

  • Classrooms:   “…our study shows that box fan air cleaners can serve as an effective low-cost alternative for mitigating airborne transmission risks in poorly ventilated spaces.”
  • Hospitals (preprint):  “A single bed hospital room equipped with an excellent ventilation rate (∼ 14 air changes per hour) can clear the aerosols in 20 minutes. However, with the addition of two air cleaners, the clearance time became 3 times faster (in 6 minutes and 30 seconds).”  
    • “What? How can there be an 14 ACH ventilation rate, but only 3 ACH to clear the aerosols? 14 ACH is every 4 mins?”
    • Answer: “An ACH is the rate to remove 63% of the air (not 100%). It requires 5x this time (5 x – 1/ACH (ie lifetime / residence time) to clear 99% (ie remaining = 0.37 ^ 5 < 0.01) of the air. Think of a drop of red dye in a sink - easy to remove the first 50% really long to remove it all."
  • Hospital (published): “With 2 small domestic air cleaners in a single patient room of a hospital ward, 99% of aerosols could be cleared within 5.5 minutes.”
  • A systemic review found:” Portable HEPA filter systems have been shown to be another effective tool in reducing viral load.”
  • CDC MMWR: “Portable HEPA air cleaners offer a simple means to increase the filtration of aerosol particles from a room without modifying the existing building ventilation system…”
  • FORD engineers did a study on a single filter version, called the Scrappy Filtration Kit..

The following Federal Agencies recommend them (along with many state public health agencies):

  • CDC directly recommends them: “Use portable high-efficiency particulate air (HEPA) fan/filtration systems to enhance air cleaning (especially in higher risk areas such as a nurse’s office or areas frequently inhabited by people with a higher likelihood of having COVID-19 and/or an increased risk of getting COVID-19).”
  • ASHRAE recommends them
  • EPA recommends them.
  • The Corsi/Rosenthal Box as discussed in the recent “Delta Schools Airborne” Webinar.
  • Media: NPR, This Old House,

If these air cleaners are so great, why haven’t any large organizations rolled them out?

They have!

At least 20,000 by the Ontario, Canada government – in classrooms, gyms, libraries with no mechanical ventilation.  As approved by their Chief Medical Officer of Health.

Toronto School District itself.

New York City, but there’s a note of caution there.  Experts have indicated that NYC did not make the best choice.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

Yes – it removes aerosols from the air.  How well does it work?  Very well.

Dr. Marwa Zaatari, Chief Science Officer at Blue Box Air & ASHRAE Associate Member

“It is the most cost effective purifier on the chart.” – this evaluation is from Dr. Zaatari, who regularly publishes an easy-to-understand chart that simplifies the often complex air clean marketplace.  It should be noted that this was the single filter version – so the 2/ 4/ 5 filter versions should perform even better.

One large caveat – this is with the shroud on the fan. 


UCDavis Western Cooling Efficiency Center found it delivers an equivalent performance to commercial air cleaners that cost 3x as much.

 

And here is the final brochure/ PDF documenting all of their work.


CBC Business Marketplace evaluated a MERV 11 single filter version of the Corsi/Rosenthal Box

The $70 single filter MERV 11 version easily outperformed the $800 Dyson Pure Hot & Cool. Even more impressively, this was with NO shroud which increases performance by 47%, and a MERV 11 filter instead of a MERV 13 filter.


The Built Environment Research Group at the Illinois Institute of Technology found these excellent results for the 4 Filter version of the Corsi/Rosenthal Box

“… (T)he Built Environment Research Group has been independently evaluating the efficacy and potential for adverse consequences…” And they evaluated this version in September 2021.

 

Why does it work so well?

Jim Rosenthal, past president of the National Air Filtration Association and chief executive officer of Tex-Air Filters, discusses why the Corsi/Rosenthal Box works so well. It’s a fascinating article, but if you have no time:

  • The sheer amount of air flow from the CR Box is about 700 CFM (on only medium speed) versus the $900 HEPA filter it was compared with (300 CFM on maximum). 
  • It must be emphasized that Jim Rosenthal called for further research into this.
  • Here’s a graph of how it performed:
  • Yes – at least as good as a $900 HEPA filter.
    • Though to be crystal clear, the CADR for the MERV 13 filters is still being measured.  
    • Above is with MERV 11 filters.  The one you will make will have MERV 13 filters, so should be better.


Dr. Richard Corsi discusses the Corsi/Rosenthal Box

In this NPR Article, Dr. Corsi reported, “”People are now reporting 600 cubic feet per minute in clean air delivery rates. That’s phenomenal. That’s better than a lot of the more expensive HEPA-based portable air cleaners,”

Speaking of Dr. Corsi – in this video he discusses the benefits of the Corsi/Rosenthal Box.

This is anecdotal – and you have to have masking as well as air cleaning!


Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.

Per Dr. Poppendieck “I actually love this question because it shows the person has thought about what we intuitively understand about our indoor environment.  We generally don’t feel the air move indoors.  Humans can sense air movement down to about 0.1 m/s (0.3 ft/s).  Below that, we generally consider the air to be “still.” Hence, there is a natural assumption that the air on the other side of the classroom won’t reach me.  But most of us have also observed particles moving in a sun beam in a room we feel is “still.”  So we intuitively think air is still, even through we have observed it moving. 

In fact, in most indoor environments air is moving around 0.05-0.1 m/s (0.15-0.3 ft/sec).  This means that if an airborne particle traveled in a straight line it could travel the length of a classroom in roughly three to five minutes. That speed is without taking into account inputs that enhance air movement (a person coughing, a person walking, the heat rising from every person, HVAC airflows, settling, thermal gradients due to sunlight). 

You already know that this is true, just think about how long it takes you to smell a cigarette that someone is smoking from across the room.  A room is much like a mixing bowl full of ingredients for making cookies.  Once we add a new ingredient to the batter and start mixing, some of the new ingredient will stick to the edge of the bowl (like the corners of a room), but most of it will evenly mix throughout the batter relatively quickly. 

But what about plumes forming when a portable air cleaner is on? Well, there will be plumes of aerosol containing viruses moving throughout the room without any filtering device present due to the all the things in a room that enhance airflow. Remember air is not still, even if you can’t feel it moving. Airborne viruses are already moving around the classroom in a time frame that is faster than the length of a one hour class.  So even without a portable air filter, everyone in the classroom will likely be exposed to the airborne viruses by the end of the class.

A portable air cleaner will slightly increase the air velocity and mixing in the room (although you won’t likely feel air going into a portable air cleaner unless you are less than ~0.5 m or 1.5 ft from the intake), while also reducing the average aerosol containing virus load in the room by 10 % – 40 % (1 micron) over the duration of the class. 

So will portable air cleaners in a classroom make the airborne virus problem worse?  Probably not since the room is fairly well mixed in the time frame of a class even without an added fan (air cleaner) and the air cleaner will reduce the average concentration of aerosols that one breaths in.  Will portable air cleaners keep me safe from COVID19 while teaching?  We can never be completely safe while not in isolation. However, portable air cleaners are one layer of a risk reduction approach to make teaching in the time of airborne viruses safer.”

Source:  http://poppendieck.com/IAQ/COVID19%20FAQ.html

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
2
0

Click here to go back to all FAQ’s.

This could not be farther from the truth.

Air cleaning is additive – not subtractive.

For example – hospitals have excellent air cleaning.  In this preprint of a study – “A single bed hospital room equipped with an excellent ventilation rate (∼ 14 air changes per hour) can clear the aerosols in 20 minutes. However, with the addition of two air cleaners, the clearance time became 3 times faster (in 6 minutes and 30 seconds).”  Explanation of why .

Don’t forget – the following agencies recommend portable air cleaners.

  • CDC directly recommends them: “Use portable high-efficiency particulate air (HEPA) fan/filtration systems to enhance air cleaning (especially in higher risk areas such as a nurse’s office or areas frequently inhabited by people with a higher likelihood of having COVID-19 and/or an increased risk of getting COVID-19).”
  • ASHRAE recommends them
  • EPA recommends them.

ASHRAE is available to consult with.

They can be emailed COVID-19@ashrae.org

Clickable link to that email address.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.

They get it and transmit it. 

They have ACE2 receptors, which SARS-COV-2 targets.  And just like adults, they have a thermal plume wafting SARS-COV-2 up to you.  Basically, our body’s own heat forms a never-ending plume of air movement upwards because heat rises.

“While there has been no systematic study on human thermal plume in the COVID-19 context, an existing body of evidence suggests that it generates constant uprising airflows around the human body and transports aerosols from lower regions into the breathing zone.”

And

” Under the constant uprising airflows, the vertical transport and human inhalation of indoor aerosols would be particularly enhanced when the emission source is located at lower horizons in proximity to the human occupant (Rim et al. 2009).”

” To summarize, there is ample evidence indicating that thermal plume creates constant uprising airflows around the human body and therefore has the ability to transport abundant quantities of airborne droplets and particles from lower regions to the human breathing zone.”

Some more interesting bits of info from that study:

  • We might be breathing in microplastics: 
    • “Vianello et al. (2019) utilized a breathing thermal manikin with respiratory patterns and metabolic heat similar to those of adult males to assess the influences of thermal plume on the human inhalation of indoor microplastics. The study found that thermal plume continuously transported microplastics from lower regions of the room into the breathing zone of the sedentary manikin. “
  • For the office:
    • “For sedentary individuals, moving their body closer to desk can partly block the uprising thermal plume and reduce its velocity entering the breathing zone (Melikov 2015; Licina et al. 2014). “
  • “Generated by body-to-air temperature gradients, human thermal plume creates persistent uprising airflows along the human boundary layer, typically as a laminar-to-turbulent flow with varying thicknesses from 2–4 mm to 200 mm and a maximum velocity of 0.2–0.3 m/s, which is comparable to the designed air velocity in various buildings with mixed ventilation under the current design criteria. “

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.

Here’s such a letter.

  • It addresses
    • Air cleaner efficacy in general, and the Corsi/Rosenthal Box, in specific.
    • HVAC infrastructure concerns (it will not cause issues).
    • Electrical concerns (will not cause fires).

How to use such a letter? Possible ideas:

  • Just emailing it to the concerned individual.
  • Better would be to find parents “…who have working relationships with district admin and/or school board members? It helps to meet with them or call them individually. I sent a letter to our superintendent and cc’d the admin folks I know. They are working on getting CR boxes now.” (Quote from DaleAnn Baker.)

How NOT to use such a letter? Some people are all about videos. That’s ok – meet them where they are at.

What if you experience push-back after the letter, or you anticipate a hard push-back? Sometimes, it helps to gather evidence of poor ventilation.

  • Get a CO2 monitor like an Aranet. Put it in your kid’s backpack pocket (this twitter thread has some ideas) – ideally, you want it where your kid is.. Track the ventilation for a couple of days. (Very important – HEPA/ DIY air cleaners will NOT lower CO2, as gas molecules are too small to be captured by the filters.).
  • What is the value of measuring CO2? This excellent Washington Post article , posted at archive.is (so all can read it), explains all.
  • If the CO2 is showing as high, then you can present that as an indicator of the ventilation as being insufficient.
    • What is considered high? Above 920 ppm (or 500 above baseline).
      • This is discussed by Dr. Dustin Poppendieck here.
        • Prepandemic times:
          • For 24 students & 1 teacher, roughly 550 ppm over the outside air (usually 420 ppm – you can find this just by putting the CO2 monitor outside the classroom). So, 970 ppm.
          • For 34 students & 1 teacher, roughly 900 ppm over outside air (1320 ppm).
          • But these are NOT those times.
      • Pandemic Recommendations – roughly 500 max over baseline. 920 PPM in most locations.
        • The Belgian Government recommends no more than 900 PPM total – so roughly 400 to 500
        • Harvard Healthy Buildings initiative (Page 27, 5-6 ACH is roughly 920 PPM as per Dr. Poppendieck).
  • Some Talking points, from this spreadsheet developed by David Elfstrom., as discussed here.
    • At 800 PPM (Parts Per Million), 1% of what everyone breathes is from other people’s lungs – which might have Covid in them. (Though some of it would be from your own lungs.).
    • At 1000 PPM, 1.5%
    • At 1200, 2.1%.
    • At 1500, 3%
  • Dr. Linsey Marr, respiratory virus transmission/aerosol scientist tracked the CO2 in her school. Make sure to read the comments.
  • Additional Resources on this topic:

Did you find this FAQ helpful?
4
0

Implementation

Click here to go back to all FAQ’s.

A simple question, but can be a complicated answer.

  • Try not to place next to a wall if possible.  You want air flow.
  • If you know who’s infected, next to them (typically placement in a patient’s hospital room).
  • If you are in a classroom, you will want 2.  Place one in the center of the room, even if you have windows open.  Place the other in the middle of the room, but up near the teacher. 

From http://poppendieck.com/IAQ/COVID19%20FAQ.html

I just bought a portable HEPA air cleaner.  Where should I put it in the classroom?  To be effective, portable air cleaners need to get as much of the air in the room through the filter as quickly as possible.  Think about trying to beat an egg in a square pan.  If you try to beat the egg with your mixing device in the corner or on an edge, the egg in the far side of the pan will not get stirred very quickly.  However, if you place the beating device in the middle of the pan, the egg will mix faster (but still not perfect in the corners). 

Likewise, in a classroom, you want to place an air cleaner as close to the middle of the room as possible, elevated up off the ground.  This will maximize the amount of air moving through the HEPA filter. Make sure you place the air cleaner in a location where it won’t fall onto someone and secure the cord to prevent any tripping hazards.

Most portable air cleaners draw air in from the sides and exit on the top.  Many Do-It-Yourself filters made with box fans and filter furnaces exhaust air to the side. These DIY designs should not be placed on the floor as the exiting air may resuspend particles from the floor that may contain viruses.

Operate your portable HEPA cleaner on its highest setting. The higher the setting, the more air that moves through the filter and lower the virus concentrations will be in the air. Hence, highest setting equals lowest risk for people in the classroom. Lower settings maybe desirable due to fan noise, but be aware they will increase risk as less air is moving through the filter.”

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
3
1

Click here to go back to all FAQ’s.

That study did not include the risk of reaersolization (blow back up in the air)  of dried respiratory aerosols that will have settled on the ground.   You will give a little in efficiency to gain safety.

http://poppendieck.com/IAQ/COVID19%20FAQ.html

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
5
4

Click here to go back to all FAQ’s.

Roughly 51 DBA..This is more quiet than a refrigerator.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

You can build one of these for just under $100, and it will help significantly remove respiratory aerosols that contain SARS-COV-2 from the air. We recommend at least 2 of them in a normal sized classroom. $200.

Keep in mind – something is better than nothing.  Even if you did the single filter build, which would be about $36 with the filter AND fan, it would help significantly reduce aerosols in the room.  

And you could save up to buy the rest of the filters, later.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Always refer to the manufacturer’s specifications.  But a general rule of thumb is:

  • If used during smoke season, 3 months.
  • If during regular usage, 6 month.

Additional details on MERV 13-A filters which for sure will are the ones that last that long.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

Put on your N100 elastomeric respirator (more comfortable than N95). Does not have to be N100 – just better masks work…better.

Carefully, pick up the Corsi/Rosenthal box and gently take it outside.

Carefully cut the filters apart, gently peel it back to get the fan off.

Separate the filters and gently place in a garbage bag.  Do not just shove them in as they might have virus in them and don’t want the garbage bag blowing the virus back on you. 

 Tie the bag tight.  Toss into garbage.

Make new box!

 Why not spray disinfectant on it?  

 Because by the time the garbage bag degrades the virus will have been inactivated.

But – this was for the original WT strain of SARS-COV-2.  Who knows what it might be for Delta.

Here are two estimates that indicate the filter environment (moving air, etc) might lead to quicker inactivation.

Since we don’t know 100% either way, just be careful.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
2
0

As discussed here, it decreases performance. The 1″ filters are fine – although you would get even better performance with 2″ filters. Just not 1″ filters doubled up.

Did you find this FAQ helpful?
1
0

Safety

Click here to go back to all FAQ’s.

I’m sorry, you do still need to wear a mask.  Why? 

For the same reasons Health Care Workers continue to get infected in hospitals which have excellent ventilation with 6 Air Changes Per Hour.

Ventilation cleans up far-field aerosols (>6 feet away), but cannot clean the air of aerosols that have just been emitted by the infected person (near-field aerosols < 6 feet away).

An example to help explain – you  are in a room with someone smoking a cigarette and an air cleaner.  You can see the smoke being removed from the air by the air cleaner.  But if the smoker blows smoke in your face, the air cleaner cannot clean it in time.

Another point:

“We put a HEPA air cleaner in our classroom.  Do I have to wear a mask in the classroom? Yes.  Think about a used diaper in a room.  What is the best way to keep the room from stinking?  It is not to open a window or put in a filter.  It is to remove the diaper from the room.  This is one of the fundamental pillars of indoor air quality: source reduction. 

Wearing a mask, even a cloth mask that isn’t perfectly fitted, will reduce the number of aerosols that get into the air from a contagious individual.  When we talk, we expel more particles that are airborne than when we are just breathing.  When we talk loud or sing, we expel even more.  Hence, even the teacher should wear a mask. Masks with clear mouth shields should be sought if people who need to lip read are present. 

The goal is a layered risk reduction.  We need to take as many actions as we can (increase ventilation, HEPA air cleaner, masks, etc.) to reduce the risk as none will completely eliminate it. Wearing masks will reduce average airborne particle load (1 micron) in the classroom by roughly 30%.”  Source.

Here’s a video that shows aerosols in general – and how plexiglass does NOT stop aerosols.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.

That study did not include the risk of reaersolization (blow back up in the air)  of dried respiratory aerosols that will have settled on the ground.   You will give a little in efficiency to gain safety.

http://poppendieck.com/IAQ/COVID19%20FAQ.html

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
5
4

Always refer to the manufacturer’s specifications.  But a general rule of thumb is:

  • If used during smoke season, 3 months.
  • If during regular usage, 6 month.

Additional details on MERV 13-A filters which for sure will are the ones that last that long.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

Put on your N100 elastomeric respirator (more comfortable than N95). Does not have to be N100 – just better masks work…better.

Carefully, pick up the Corsi/Rosenthal box and gently take it outside.

Carefully cut the filters apart, gently peel it back to get the fan off.

Separate the filters and gently place in a garbage bag.  Do not just shove them in as they might have virus in them and don’t want the garbage bag blowing the virus back on you. 

 Tie the bag tight.  Toss into garbage.

Make new box!

 Why not spray disinfectant on it?  

 Because by the time the garbage bag degrades the virus will have been inactivated.

But – this was for the original WT strain of SARS-COV-2.  Who knows what it might be for Delta.

Here are two estimates that indicate the filter environment (moving air, etc) might lead to quicker inactivation.

Since we don’t know 100% either way, just be careful.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
2
0

Click here to go back to all FAQ’s.

Per Dr. Poppendieck “I actually love this question because it shows the person has thought about what we intuitively understand about our indoor environment.  We generally don’t feel the air move indoors.  Humans can sense air movement down to about 0.1 m/s (0.3 ft/s).  Below that, we generally consider the air to be “still.” Hence, there is a natural assumption that the air on the other side of the classroom won’t reach me.  But most of us have also observed particles moving in a sun beam in a room we feel is “still.”  So we intuitively think air is still, even through we have observed it moving. 

In fact, in most indoor environments air is moving around 0.05-0.1 m/s (0.15-0.3 ft/sec).  This means that if an airborne particle traveled in a straight line it could travel the length of a classroom in roughly three to five minutes. That speed is without taking into account inputs that enhance air movement (a person coughing, a person walking, the heat rising from every person, HVAC airflows, settling, thermal gradients due to sunlight). 

You already know that this is true, just think about how long it takes you to smell a cigarette that someone is smoking from across the room.  A room is much like a mixing bowl full of ingredients for making cookies.  Once we add a new ingredient to the batter and start mixing, some of the new ingredient will stick to the edge of the bowl (like the corners of a room), but most of it will evenly mix throughout the batter relatively quickly. 

But what about plumes forming when a portable air cleaner is on? Well, there will be plumes of aerosol containing viruses moving throughout the room without any filtering device present due to the all the things in a room that enhance airflow. Remember air is not still, even if you can’t feel it moving. Airborne viruses are already moving around the classroom in a time frame that is faster than the length of a one hour class.  So even without a portable air filter, everyone in the classroom will likely be exposed to the airborne viruses by the end of the class.

A portable air cleaner will slightly increase the air velocity and mixing in the room (although you won’t likely feel air going into a portable air cleaner unless you are less than ~0.5 m or 1.5 ft from the intake), while also reducing the average aerosol containing virus load in the room by 10 % – 40 % (1 micron) over the duration of the class. 

So will portable air cleaners in a classroom make the airborne virus problem worse?  Probably not since the room is fairly well mixed in the time frame of a class even without an added fan (air cleaner) and the air cleaner will reduce the average concentration of aerosols that one breaths in.  Will portable air cleaners keep me safe from COVID19 while teaching?  We can never be completely safe while not in isolation. However, portable air cleaners are one layer of a risk reduction approach to make teaching in the time of airborne viruses safer.”

Source:  http://poppendieck.com/IAQ/COVID19%20FAQ.html

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
2
0

Click here to go back to all FAQ’s.

No:

Did you find this FAQ helpful?
3
2

Click here to go back to all FAQ’s.

This is with the Utilitech 20″ Box fan – 58 Watts when cranked to max, as measured by Jim Rosenthal.  The measurements below are for:

  • No filter attached.
  • 1 filter attached – 1″, 2″, 4″
  • Box filter – the full Corsi/Rosenthal Box attached.

This with the Lasko 20″ Box Fan – 89 Watts when cranked to max.

Exactly. The fan on high for the Corsi/Rosenthal box used 54 watts. The ELGIT air cleaner (also known as a Banker’s Lamp) used 60 watts. Just in case someone doubts the data – here are the pictures. https://t.co/jpK81qqa2F pic.twitter.com/ysLQKGvSmh — Jim Rosenthal (@JimRosenthal4) August 26, 2021

David Elfstrom also measured both with the shroud on the single filter version, which makes the fan operate more efficiently.

Utilitech/Hurricane with 13.5″ shroud: 350 CFM, 52 W! 

Lasko with 15″ shroud: 350 CFM, 74 W !

Sources:

Optimization so far, with 3M Filtrete 1900 20x20x1

Lasko with 15″ shroud: 350 CFM, 74 W

Utilitech with 13.5″ shroud: 350 CFM, 52 W!

Actual flow will be slightly higher when measured at outlet with backpressure compensation feature in the flow capture hood. /14 — David Elfstrom (@DavidElfstrom) August 16, 2021

Optimization so far, with 3M Filtrete 1900 20x20x1

Lasko with 15″ shroud: 350 CFM, 74 W

Utilitech with 13.5″ shroud: 350 CFM, 52 W!

Actual flow will be slightly higher when measured at outlet with backpressure compensation feature in the flow capture hood. /14 — David Elfstrom (@DavidElfstrom) August 16, 2021

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

This could not be farther from the truth.

Air cleaning is additive – not subtractive.

For example – hospitals have excellent air cleaning.  In this preprint of a study – “A single bed hospital room equipped with an excellent ventilation rate (∼ 14 air changes per hour) can clear the aerosols in 20 minutes. However, with the addition of two air cleaners, the clearance time became 3 times faster (in 6 minutes and 30 seconds).”  Explanation of why .

Don’t forget – the following agencies recommend portable air cleaners.

  • CDC directly recommends them: “Use portable high-efficiency particulate air (HEPA) fan/filtration systems to enhance air cleaning (especially in higher risk areas such as a nurse’s office or areas frequently inhabited by people with a higher likelihood of having COVID-19 and/or an increased risk of getting COVID-19).”
  • ASHRAE recommends them
  • EPA recommends them.

ASHRAE is available to consult with.

They can be emailed COVID-19@ashrae.org

Clickable link to that email address.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.

This is a great question!  Two part answer.  

First part is that it’s actually two different technologies.  Bulbs are usually used to clean items in a sealed container in a hospital.

Hospitals use UVGI to clean the air.  And it can be extremely effective.  Here’s respiratory virus transmission expert, Dr. Don Milton (MD, PhD) …” min 20 to max 1000 equivalent ACH. ”  Hospitals have excellent ventilation at 6 Air Changes Per Hour, so 20 ACH is phenomenal.  But, it’s an entirely different technology than bulbs.

2nd part, per David Elfstrom, IAQ expert, the bulbs will damage the filters and the air moves too fastSame basic response from Jim Rosenthal, also IAQ expert.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
1

Click here to go back to all FAQ’s.

It is recommended not to – the virus might be on the filters – but It is far more likely that airborne transmission will occur.

The odds of transfer from the filters to the hands and then to the mucosal regions of eyes, mouth, or nose are very, very low.

  • The filter is actually a 3 dimensional matrix, the virii might not be on the top level. 
  • This is a very inhospitable environment for viruses.  The constant air movement should result in quick virus inactivation.
  • For infection to happen, you would have to have transfer of infectious virus from the filter to the hand.  Then, from the hand to the face’s mucosal regions (eyes, nose, mouth).  Possible, but extremely unlikely.
    • Especially when you consider finger print ridges vary in width from 100 µm, for very thin ridges, to 300 µm for thick ridges. You would have to be extraordinarily unlucky for the 1 -5 µm respiratory aerosols to be land square on a ridge. Since there are valleys as well, which take up 50% of the space on your finger (eliminating that 50%). Below a microscopic close-up of the the fingertips.
    • You might object and say – what about norovirus? True, but different virus. For CoVid, there are just count-on-one hand few reports of fomite infection. Whereas there are 100’s of airborne transmission.

But there are some options below to prevent touch. These which will result in a less efficient air cleaner.  How much less efficient? Impossible to tell without access to specific testing equipment.

Here are some ideas if you are dead-set on this:

This one is very well done – but would result in an even great inefficiency of the air cleaner.  (It is welded together).

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

Here’s such a letter.

  • It addresses
    • Air cleaner efficacy in general, and the Corsi/Rosenthal Box, in specific.
    • HVAC infrastructure concerns (it will not cause issues).
    • Electrical concerns (will not cause fires).

How to use such a letter? Possible ideas:

  • Just emailing it to the concerned individual.
  • Better would be to find parents “…who have working relationships with district admin and/or school board members? It helps to meet with them or call them individually. I sent a letter to our superintendent and cc’d the admin folks I know. They are working on getting CR boxes now.” (Quote from DaleAnn Baker.)

How NOT to use such a letter? Some people are all about videos. That’s ok – meet them where they are at.

What if you experience push-back after the letter, or you anticipate a hard push-back? Sometimes, it helps to gather evidence of poor ventilation.

  • Get a CO2 monitor like an Aranet. Put it in your kid’s backpack pocket (this twitter thread has some ideas) – ideally, you want it where your kid is.. Track the ventilation for a couple of days. (Very important – HEPA/ DIY air cleaners will NOT lower CO2, as gas molecules are too small to be captured by the filters.).
  • What is the value of measuring CO2? This excellent Washington Post article , posted at archive.is (so all can read it), explains all.
  • If the CO2 is showing as high, then you can present that as an indicator of the ventilation as being insufficient.
    • What is considered high? Above 920 ppm (or 500 above baseline).
      • This is discussed by Dr. Dustin Poppendieck here.
        • Prepandemic times:
          • For 24 students & 1 teacher, roughly 550 ppm over the outside air (usually 420 ppm – you can find this just by putting the CO2 monitor outside the classroom). So, 970 ppm.
          • For 34 students & 1 teacher, roughly 900 ppm over outside air (1320 ppm).
          • But these are NOT those times.
      • Pandemic Recommendations – roughly 500 max over baseline. 920 PPM in most locations.
        • The Belgian Government recommends no more than 900 PPM total – so roughly 400 to 500
        • Harvard Healthy Buildings initiative (Page 27, 5-6 ACH is roughly 920 PPM as per Dr. Poppendieck).
  • Some Talking points, from this spreadsheet developed by David Elfstrom., as discussed here.
    • At 800 PPM (Parts Per Million), 1% of what everyone breathes is from other people’s lungs – which might have Covid in them. (Though some of it would be from your own lungs.).
    • At 1000 PPM, 1.5%
    • At 1200, 2.1%.
    • At 1500, 3%
  • Dr. Linsey Marr, respiratory virus transmission/aerosol scientist tracked the CO2 in her school. Make sure to read the comments.
  • Additional Resources on this topic:

Did you find this FAQ helpful?
4
0

General Questions

Click here to go back to all FAQ’s.

Better.  NYC’s CADR for smoke was 129.  The Corsi/Rosenthal Box CADR was 132. And that was with MERV 10/11 filters.  The Corsi/Rosenthal Box should be made with MERV 13 filters, so will test even higher. These measurements are in process.

Did you find this FAQ helpful?
1
0

Click here to go back to all FAQ’s.

Laborious Experimentation – drop him a “like” on Twitter!  Scroll up on this thread to see his excellent work!


And this optimization thread (scroll up):


Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

Maybe 🙂 .

This is page is really just a collection of ideas to help inspire YOU.  

It was conceived as a combination of physics (aerosols), biology (lungs), and math (large number conversions).  All parts are meant to be used separately or together.  

For now, just going to lay out the experiments, if you write out introductions and want to contribute a write-up such as “What are aerosols”, please contact @lazaruslong13 on Twitter.

Aerosols Introduction

After discussing, show this video of 50 micron aerosols.  Afterwards, you can have them visualize dust motes caught in a sunbeam in their living room – those are approximately 50 micron aerososl as well.

Much discussion lately in aerosol/disease transmission communities about the “5 micron cutoff” where droplets supposedly fall to ground w/in 1-2 m. @jljcolorado and @linseymarr has suggested ~50 microns.

Here’s some video evidence for that. 50 micron droplets wafting in lab… pic.twitter.com/5SrE7GeKDF — Ryan Davis (@MicroLevitator) July 16, 2020

Fun Aerosol Demonstration Option 1

Smoke machine plus garbage can vortex…demonstrating aerosols, and Bernoulli’s Principle

OR

Fun Aerosol Demonstration Option 2 – this one HAS to be outside.

Cheap Aerosol Demonstration – Get a little flour and blow into the air – those are aerosols.  

Lungs (Biology)

From here.  Materials required are here – the lung demonstration is very well laid out on their web page.

And while doing the above experiment, or before, you can talk about about fun lung facts from the below two articles.  What you see is just a sample of the fascinating knowledge in them.

After talking about the gallons breathed, you could segue into…

Math 

Your lungs process over 2,000 gallons of air. Per day. Very rough math follows  (please feel free to contact me to get it corrected!)

If a respiratory aerosol is 5 microns, that would be 1.51416e+18 aerosols processed. 1,514,160,000,000,000,000. Potentially, 1.5 quintillion 5 micron aerosols.

So, we don’t want  a bunch of aerosols in our lungs, so what  do we do?  Clean the air.

Corsi/ Rosenthal Box Science

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

This is a great question!  Two part answer.  

First part is that it’s actually two different technologies.  Bulbs are usually used to clean items in a sealed container in a hospital.

Hospitals use UVGI to clean the air.  And it can be extremely effective.  Here’s respiratory virus transmission expert, Dr. Don Milton (MD, PhD) …” min 20 to max 1000 equivalent ACH. ”  Hospitals have excellent ventilation at 6 Air Changes Per Hour, so 20 ACH is phenomenal.  But, it’s an entirely different technology than bulbs.

2nd part, per David Elfstrom, IAQ expert, the bulbs will damage the filters and the air moves too fastSame basic response from Jim Rosenthal, also IAQ expert.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
1
1

Click here to go back to all FAQ’s.

Simple question, complicated answer. First one – assuming you have an air cleaner – the time it takes to do 3 air changes. Source:

 

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

Here’s such a letter.

  • It addresses
    • Air cleaner efficacy in general, and the Corsi/Rosenthal Box, in specific.
    • HVAC infrastructure concerns (it will not cause issues).
    • Electrical concerns (will not cause fires).

How to use such a letter? Possible ideas:

  • Just emailing it to the concerned individual.
  • Better would be to find parents “…who have working relationships with district admin and/or school board members? It helps to meet with them or call them individually. I sent a letter to our superintendent and cc’d the admin folks I know. They are working on getting CR boxes now.” (Quote from DaleAnn Baker.)

How NOT to use such a letter? Some people are all about videos. That’s ok – meet them where they are at.

What if you experience push-back after the letter, or you anticipate a hard push-back? Sometimes, it helps to gather evidence of poor ventilation.

  • Get a CO2 monitor like an Aranet. Put it in your kid’s backpack pocket (this twitter thread has some ideas) – ideally, you want it where your kid is.. Track the ventilation for a couple of days. (Very important – HEPA/ DIY air cleaners will NOT lower CO2, as gas molecules are too small to be captured by the filters.).
  • What is the value of measuring CO2? This excellent Washington Post article , posted at archive.is (so all can read it), explains all.
  • If the CO2 is showing as high, then you can present that as an indicator of the ventilation as being insufficient.
    • What is considered high? Above 920 ppm (or 500 above baseline).
      • This is discussed by Dr. Dustin Poppendieck here.
        • Prepandemic times:
          • For 24 students & 1 teacher, roughly 550 ppm over the outside air (usually 420 ppm – you can find this just by putting the CO2 monitor outside the classroom). So, 970 ppm.
          • For 34 students & 1 teacher, roughly 900 ppm over outside air (1320 ppm).
          • But these are NOT those times.
      • Pandemic Recommendations – roughly 500 max over baseline. 920 PPM in most locations.
        • The Belgian Government recommends no more than 900 PPM total – so roughly 400 to 500
        • Harvard Healthy Buildings initiative (Page 27, 5-6 ACH is roughly 920 PPM as per Dr. Poppendieck).
  • Some Talking points, from this spreadsheet developed by David Elfstrom., as discussed here.
    • At 800 PPM (Parts Per Million), 1% of what everyone breathes is from other people’s lungs – which might have Covid in them. (Though some of it would be from your own lungs.).
    • At 1000 PPM, 1.5%
    • At 1200, 2.1%.
    • At 1500, 3%
  • Dr. Linsey Marr, respiratory virus transmission/aerosol scientist tracked the CO2 in her school. Make sure to read the comments.
  • Additional Resources on this topic:

Did you find this FAQ helpful?
4
0

As discussed here, it decreases performance. The 1″ filters are fine – although you would get even better performance with 2″ filters. Just not 1″ filters doubled up.

Did you find this FAQ helpful?
1
0

Country Specific

Click here to go back to all FAQ’s.

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Click here to go back to all FAQ’s.

 

Click here to go back to all FAQ’s.

Did you find this FAQ helpful?
0
0

Related posts

SchoolIAQ fact sheet series
Indoor Air Quality Fact Sheet Series

The Center for Green Schools at U.S. Green Building Council has released a unique series of fact sheets about indoor air quality (IAQ), designed to help people without a technical …

air filters work
Air filters work – EPA, CDC, OSHA, ASHRAE, and more agree.

We know that HEPA and MERV13 filters work to remove airborne virus particles. Read all about it from the EPA, CDC, OSHA, and ASHRAE.

Portable Air Cleaners comparison graph, HEPA, MERV13, CADR, cost, db decibels noise
Portable Air Cleaner (HEPA filter) buying guide

Buying guides by Air Quality expert Marwa Zaatari (includes room size, noise level and cost) the California Air Resources Board (CARB), Association of Home Appliance Manufacturers (AHAM) and a DIY opt…

Box Fan filter - Corsi Rosenthal Box air filter
DIY box fan air filters – Corsi-Rosenthal box

Also known as a Corsi-Rosenthal box, this DIY method of building your own air filter with MERV13 furnace filters and a box fan are an easy and cost-effective way to help clear indoor air from airborne…

box fan filter FAQ
Corsi/Rosenthal Box FAQ

Answers to the most frequently asked questions regarding the DIY box fan air filter solution, also known as the Corsi-Rosenthal box.