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Eric Feigl-Ding Profile picture
@DrEricDing
Feb 19, 2021 • 30 tweets • 14 min read • Read on X
📍Pardon my vent about insufficient ventilation / air exchange & school policy. Air exchange (via fresh air or disinfection) is really important for reducing #COVID19 transmission—we should aim for 5-6 air exchanges per hour. Achieving 5-6 is harder, but should we give up? No!🧵 Image
2) President Kennedy once said, we choose to goto the moon 🌙 not because it is easy, but because they are hard—and important. Some think asking for sufficient school ventilation is like asking schools to goto the moon. No, not true! It’s possible. We can do it.
3) First there are ways to ventilate without HEPA filters or full windows. You can even with 1 door. 2 doors better. Here is how to ventilate your school classrooms if unable to open window. #COVID19
4) Notably in a room with just 1 door, use 2 fans—one high and one low to the ground blowing in opposite directions. See video above for details.
5) But many classrooms have HEPA filters are a good bet. If your classroom has only 2 ACH (air exchanges) per hour, you can bump it up to 5 with a HEPA filter! *Depending on room size of course. Some rooms will need 2 HEPA filters.
6) the best HEPA filter discussion thread is by Dr @CorsIAQ - a well regarded aerosol scientist.
7) I won’t go too much into Upper air UV at the moment, even though they definitely do work — they are better for larger room rooms like auditoriums, gymnasiums, multipurpose rooms, and cafeterias. And they can achieve 15 ACH per hour which is better than airplanes ~10 ACH/hour.
8) But i won’t discuss too much on upper air UV because costs are variable and schools should focus on ventilation and HEPA filters first. And is there funding support? Yes soon in the Biden COVID Bill—$130 Billion for school reopening. google.com/amp/s/www.vox.… Image
9) $130 billion for schools is a good start. But there are 13,000 K-12 schools in the US. So about 10 million per school, but not all for ventilation and air quality obviously—but a large sum of that should be for air quality, not for plexiglass dividers! guide2research.com/research/ameri…
10) Notably lacking emphasis though is ventilation and airborne precautions in the latest CDC guidelines. CDC did mention it but it was buried in the details and not reinforced much.
11) The science on airborne virus and need for ventilation is there. Leading scientist have writing a strong letter to @CDCDirector @JeffZients of @WHCOVIDResponse and Fauci to add more guidance on ventilation and premium masks. drive.google.com/file/d/1O5zd_J… Image
12) Notably, they ask:

đź“Ś Update and strengthen CDC guidelines to fully address transmission via inhalation exposure to small inhalable particles from infectious sources at close, mid and longer range. Updated guidelines should be informed by a risk assessment model that focuses
13) on source & pathway (ventilation) controls first, followed by respiratory protection. Workers in the highest risk categories, including all healthcare workers and other workers with prolonged, close contact with infectious people, must also be provided respiratory protection.
14) The scientists @RickABright @kprather88 @celinegounder @linseymarr @Don_Milton @mtosterholm @robertschooley very politely but strongly ask for these airborne safety measures and updates to be made. drive.google.com/file/d/1O5zd_J… Image
15) Premium masks, we should switch to, but that is outside of individual school control. But what is not outside school board control is what we can do to invest in air quality and air exchanges. Dr @CorsIAQ says the cost of a HEPA is just $10 per student, plus $3 per year!
16) Let that sink in — roughly $10/student initial investment and then just $3/student per year for every classroom to get a portable HEPA filter!!! That is not too much ask! And the Biden bill’s 130 billion for schools has more than enough for HEPA & other advanced upgrades.
17) Also, some say getting 4 ACH is good enough. Why stop at just 4? Why not get a second HEPA filter for larger classrooms or high density rooms? Or if unable to afford HEPA, use a Jerry rigged “Corsi Box”! Image
18) What is this “Corsi Box” you ask? Good question. It’s named after famed aerosol engineering professor @CorsIAQ of course, and it is 1 simple box fax + 5 MERV13 air filters—two 16X20X2 and three 20X20X2 inches + cheap box fan!

texairfilters.com/a-variation-on…
19) It’s quite simple. You take these MERV13 grade filters that can filter out virus aerosols, and tape them up together tight like this.... ImageImage
20) “So how did “Corsi Box Fan with 5 MERV 13 Filters” Air Cleaner perform? Great. Airflow from the fan was 580 feet per minute. Box ensures more surface area of the filter media – better air flow with minimal strain on the fan motor. Plus the filters will last for 6 months” Image
21) Small additional note on the CORSI BOX.... because of air leakage on the corner of the box fan—use a “fan shroud” like this. It will improve air flow and filtration. Cut it out of simple cardboard.

texairfilters.com/how-to-improve… ImageImage
22) By adding the “fan shroud” (also used in automotive engineering), here is an enhanced Corsi Box. Total cost is well under <$50. And lasts a long time. And provides good MERV13 filtration. WIRED has a longer article—but the CORSI BOX is the best design. google.com/amp/s/www.wire… Image
23) The Wired articles goes into the details of the history and filtration engineering, and goes into CADR—"clean air delivery rate" (CADR), a combination of efficiency of the filter in pulling gunk out of the air and speed of air pushed through system.
google.com/amp/s/www.wire…
24) “CADR conveys that in cubic feet per minute—researchers now recommend five complete change-outs of the air in a classroom every hour. So ideally, you’d use the cubic footage of the room and the CADR of the filter setup to figure out how big a purifier, or how many, you need”
25) So the Corsi Box is calculated with that particular box fan to pull 580 feet of air per minute — then multiply by the size of the fan.... to get the volume flow rate. Then calculate the size of the room. Then divide to see if you can achieve 5 ACH or more.
26) also important is CO2 sensors. It’s not the CO2 per se that’s risky, it’s a proxy for ventilation. We want CO2 levels as close to fresh air of ~400, so optimally <450 parts per million. When a parent put one on his child, he saw it spike up over 1000–meaning poor indoor air.
27) in environmental health, there is a common phrase we often Use—“THE SOLUTION TO POLLUTION IS DILUTION”. The pollutant is the virus aerosols. The dilution is the ventilation / air cleanings. Make sure u have a CO2 meter to check fresh air.

google.com/amp/s/www.wash…
28) Typo in post #9– there are 130,000 K-12 schools in the US. So it would be about $1 million per school for COVID safety assistance in the Democratic House bill— a reconciliation bill that only needs simple majority and bypasses Cloture / filibuster. So good chance of passage!
29) “Until we recognise that #COVID19 is airborne we are setting ourselves up for repeated failure”

P.s. they don’t use masks in video because Australia 🇦🇺 is at almost #ZeroCovid #COVIDisAirborne

30) new recent study on portable HEPA filters and #COVID19 risk.... huge difference.

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More from @DrEricDing

Eric Feigl-Ding Profile picture
Jun 16
📍 THE 17 FIRED MEMBERS OF CDC’s VACCINE ADVISORY COMMITTEE (ACIP) speak out…

📍“As former ACIP members, we are deeply concerned that these destabilizing decisions, made without clear rationale, may roll back the achievements of US immunization policy, impact people’s access to lifesaving vaccines, and ultimately put US families at risk of dangerous and preventable illnesses.” 🔥

Full text:

Vaccines are one of the greatest global public health achievements. Vaccine recommendations have been critical to the global eradication of smallpox and the elimination of polio, measles, rubella, and congenital rubella syndrome in the US. They have also dramatically decreased cases of hepatitis, meningitis, mumps, pertussis (whooping cough), pneumonia, tetanus, and varicella (chickenpox), and prevented cancers caused by hepatitis B virus and human papillomaviruses.1 Recent scientific advancements enabled the accelerated development, production, and evaluation of COVID-19 vaccines, leveraging novel technologies that are estimated to have prevented approximately 1.6 million hospitalizations and 235 000 deaths in the US alone.2
For more than 60 years, the Advisory Committee on Immunization Practices (ACIP)—codified in the federal regulations (42 USC 217a: advisory councils or committees)—has served as a panel of experts that reviews the most up-to-date evidence on vaccines and monoclonal antibodies (eg, against respiratory syncytial virus [RSV]), providing sound recommendations to the US Centers for Disease Control and Prevention (CDC) regarding how vaccines should be used. ACIP recommendations are the cornerstone of the immunization program in this country. First, they serve as guidance and are the national standard for the use of Food and Drug Administration (FDA) authorized and licensed vaccines, providing a unified and trusted approach to vaccinations for the diverse array of immunization providers across the US. Second, they ensure science-based and tested immunization schedules that are optimized for well-timed protection against serious diseases. Third, the recommendations affect insurance coverage and safeguard broad access for vaccines. Fourth, ACIP’s continued monitoring of disease epidemiology and scrutiny of vaccine safety inform timely updates to recommendations that have maintained the trust and protection of the population. This transparent and ongoing surveillance of vaccines is one of the most stringent around the world, historically making the deliberations and decisions of this committee a beacon for immunization programs globally, while also serving as the foundation for recommendations harmonized with leading medical organizations in the US.3,4
ACIP committee members have always been selected through a rigorous process based on their expertise in immunology, epidemiology, pediatrics, obstetrics, internal and family medicine, geriatrics, infectious diseases, and public health. Historically, committee members were chosen because they worked at hospitals, clinics, health departments, universities, and other organizations where they dedicated themselves to caring for patients, conducting research, and helping to prevent and treat infectious diseases. Members’ deep understanding of immunization issues ensured that vaccine policies were grounded in scientific evidence, aligned with the needs of economically, socially, and medically diverse US communities, and always considered the public value, trust, and acceptability of vaccines.
Despite recent suggestions to the contrary, health care providers and the US public trust ACIP. For the past 18 years, the National Immunization Survey has shown that 99 of every 100 children in the US have received at least some recommended vaccines by 2 years of age, consistent with acceptance of ACIP recommendations implemented by trusted clinicians (National Immunization Survey - Childof Healthy People 2030).…Image
2) Full text part 2:

This does not suggest the population is so distrustful that it warrants dismantling the process by which vaccines have been recommended. ACIP standard procedures have minimized the risk of alleged conflicts of interest and biases. For decades, members of ACIP have undergone a thorough application and review process to participate. Proposed members submitted letters of support from other known experts and peers, completed an interview process, underwent a background check, and disclosed financial interests that might be considered a conflict, including any professional or financial relationships of immediate family members. Historically, it has taken up to 2 years for nominees to be approved to join ACIP.
Once part of the committee, ACIP members spent significant time preparing for meetings, reviewing the scientific evidence, and chairing work groups that, along with many CDC public health officials, led to the final recommendations that were determined during public meetings, which also included opportunities for public comment. Recordings of these meetings, agendas, and presentations were publicly available. Additionally, members agreed to ongoing monitoring and disclosure throughout their tenure. For example, potential conflicts of interest were reviewed throughout their time on the committee. Statements about potential conflicts were required during each meeting and before each vote, and members recused themselves from voting if any conflicts were identified. These disclosures have also recently been posted on the CDC website for public scrutiny. ACIP was among the most stringent and transparent of the federal committees, and we hope those criteria will apply to any new members joining the committee.
The abrupt dismissal of the entire membership of the ACIP, along with its executive secretary, on June 9, 2025, the appointment of 8 new ACIP members just 2 days later, and the recent reduction of CDC staff dedicated to immunizations have left the US vaccine program critically weakened.5,6 These actions have stripped the program of the institutional knowledge and continuity that have been essential to its success over decades. Notably, the ACIP charter specifies that committee members serve overlapping terms to ensure continuity and avoid precisely the disruption that will now ensue. The termination of all members and its leadership in a single action undermines the committee’s capacity to operate effectively and efficiently, aside from raising questions about competence.
Compounding these concerns, recent changes to COVID-19 vaccine policy, made directly by the HHS secretary and released on social media, appear to have bypassed the standard, transparent, and evidence-based review process.7 Such actions reflect a troubling disregard for the scientific integrity that has historically guided US immunization strategy. The newly stated strategy to replace ACIP members with individuals who will “exercise independent judgment, refuse to serve as a rubber stamp, and foster a culture of critical inquiry” is already leading to warnings by academic and scientific institutions, professional organizations, and the public who for decades have known well that these sought-after qualities precisely characterized the now-dismissed members of the ACIP.5
3) Part 3:

As former ACIP members, we are deeply concerned that these destabilizing decisions, made without clear rationale, may roll back the achievements of US immunization policy, impact people’s access to lifesaving vaccines, and ultimately put US families at risk of dangerous and preventable illnesses. Vaccines and the anti-RSV monoclonal antibodies are lifesaving, and people in the US deserve to have recommendations and broad access to use them to prevent serious diseases. In this age of government efficiency, the US public needs to know that the routine vaccination of approximately 117 million children from 1994-2023 likely prevented around 508 million lifetime cases of illness, 32 million hospitalizations, and 1 129 000 deaths, at a net savings of $540 billion in direct costs and $2.7 trillion in societal costs.8Finally, as individuals, we remain committed to evidence-based vaccine policy, both through our ongoing work in immunization science, public health, and medical education, and by supporting future efforts to keep America healthy that uphold scientific rigor and the public’s trust.
Read 4 tweets
Eric Feigl-Ding Profile picture
May 8
⚠️Tariffs On Medications Will Make America Sick

We might soon see the Trump WH impose tariffs on pharmaceuticals—patients will suffer and die.

During the past few weeks, President Trump’s on-again, off-again tariff wars have rattled the stock market, decimated many Americans’ retirement funds, and promised to send grocery prices soaring—and his administration hasn’t even gotten to critical pharmaceutical tariffs yet. But that will likely be the next shoe to drop.
Trump exempted pharmaceuticals from his first round of tariffs in early April, but recently declared that he intends to impose “a major tariff” on imported medicines “very shortly.” These tariffs, he claims, will prompt pharmaceutical companies to leave countries including China and India and begin “opening up their plants all over the place.”
Commerce Secretary Howard Lutnick said in a television interview in mid-April that these tariffs are coming in the “next month or two.”

What will this mean? 

Read on:
progressive.org/op-eds/tariffs…Image
2) The majority of brand name drugs used in the United States are imported. Even generic drugs often rely on ingredients and direct imports from China, including pain relievers and cardiovascular drugs used by millions.
3) The United States was already facing a drug shortage crisis before Trump’s tariff announcement. Now, his policies will drive upnot only the cost of medicines, but also other health care items such as X-ray machines and medical instruments.
Read 8 tweets
Eric Feigl-Ding Profile picture
Apr 10
It’s a trap: CATCH 22—if you register, ICE will deport you. If you don’t register, you’ve now committed a crime for the first time, and ICE will deport you. Trump doesn’t care if you’ve paid all taxes and followed all laws—ICE will deport you.

apnews.com/article/illega…Image
2) The Department of Homeland Security announced that it was mandating that all people in the United States illegally register with the federal government, and said those who didn’t self-report could face fines or prosecution. ***Failure to register is considered a crime***
3) Registration will be mandatory for everyone 14 and older without legal status. People registering have to provide their fingerprints and address, and parents and guardians of anyone under age 14 must ensure they registered. The registration process also applies to Canadians who are in the U.S. for more than 30 days, such as so-called snowbirds who spend winter months in places like Florida.
Read 4 tweets
Eric Feigl-Ding Profile picture
Apr 3
Now economists know how scientists felt back when he pushed “hydroxychloroquine”
2) HCQ preventing COVID deaths has been debunked— and it’s now been linked with deaths.

@JoshuaPCohen1
forbes.com/sites/joshuaco…Image
@JoshuaPCohen1 3) JPMorgan on Trump Tariffs: “The largest tax increase since 1968” Image
Read 6 tweets
Eric Feigl-Ding Profile picture
Mar 28
My god—Earthquake (a Richter ~7.7) causes a skyscraper to collapse in Bangkok. Hope all the construction workers made it out.
2) this skyscraper collapse was captured from a distant car’s dashcam while on a highway

3) another view of the collapse. For those who lived through 9/11, this collapse is a bit triggering.
Read 5 tweets
Eric Feigl-Ding Profile picture
Mar 27
Welp—kiss public health & medical research infrastructure in America goodbye for the next 4 years. RFK Jr plans to cut 10,000 jobs from Trump HHS. Image
2) this will not make America healthy again… not by a long shot. So dangerous and irresponsible.
3) “Kennedy is set to announce Thursday the planned changes, which include axing 10,000 full-time employees spread across departments tasked with responding to disease outbreaks, approving new drugs, providing insurance for the poorest Americans and more”.
Read 5 tweets

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