Dr. Rancourt: Masks and Respirators Do Not Work – A Review of Science Relevant to Curbing Covid-19 Transmission

Dr. Dennis Rancourt, PhD

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Dr. Dennis Rancourt – May 20, 2020 – A Ph.D from University of Toronto (1984), and is a former professor of physics.
Masks and respirators do not work. There have been extensive randomized controlled trial (RCT) studies, and meta-analysis reviews of RCT studies, which all show that masks and respirators do not work to prevent respiratory influenza-like illnesses, or respiratory illnesses believed to be transmitted by droplets and aerosol particles. Furthermore, the relevant known physics and biology, which I review, are such that masks and respirators should not work. It would be a paradox if masks and respirators worked, given what we know about viral respiratory diseases: The main transmission path is long-residence-time aerosol particles (< 2.5 μm), which are too fine to be blocked, and the minimum-infective-dose is smaller than one aerosol particle. The present paper about masks illustrates the degree to which governments, the mainstream media, and institutional propagandists can decide to operate in a science vacuum, or select only incomplete science that serves their interests. Such recklessness is also certainly the case with the current global lockdown of over 1 billion people, an unprecedented experiment in medical and political history.


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Conclusion Regarding that Masks Do Not Work

No RCT study with verified outcome shows a benefit for HCW or community members in
households to wearing a mask or respirator. There is no such study. There are no exceptions.
Likewise, no study exists that shows a benefit from a broad policy to wear masks in public
(more on this below).
Furthermore, if there were any benefit to wearing a mask, because of the blocking power
against droplets and aerosol particles, then there should be more benefit from wearing a
respirator (N95) compared to a surgical mask, yet several large meta-analyses, and all the RCT,
prove that there is no such relative benefit.
Masks and respirators do not work.

Precautionary Principle Turned on Its Head with Masks

In light of the medical research, therefore, it is difficult to understand why public-health
authorities are not consistently adamant about this established scientific result, since the
distributed psychological, economic and environmental harm from a broad recommendation to
wear masks is significant, not to mention the unknown potential harm from concentration and
distribution of pathogens on and from used masks. In this case, public authorities would be
turning the precautionary principle on its head (see below).

Physics and Biology of Viral Respiratory Disease and of Why Masks Do Not Work

In order to understand why masks cannot possibly work, we must review established
knowledge about viral respiratory diseases, the mechanism of seasonal variation of excess
deaths from pneumonia and influenza, the aerosol mechanism of infectious disease
transmission, the physics and chemistry of aerosols, and the mechanism of the so-called


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UK: NHS Staff Forbidden From Speaking Out Publicly About Coronavirus

In addition to pandemics that can occur anytime, in the temperate latitudes there is an extra

burden of respiratory-disease mortality that is seasonal, and that is caused by viruses. For

example see the review of influenza by Paules and Subbarao (2017). This has been known for a
long time, and the seasonal pattern is exceedingly regular.
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