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From: pzavon**At_Symbol_Here**ROCHESTER.RR.COM
Subject: Re: [DCHAS-L] Respirator physicals?
Date: Aug 14, 2020 02:20 UTC
Reply-To:
ACS Division of Chemical Health and Safety
In-Reply-To: Re: [DCHAS-L] Respirator physicals?
You are correct, but Roger was talking about the use of face masks as source control, not filtration of ventilation systems.
Peter Zavon, CIH
Penfield, NY
PZAVON**At_Symbol_Here**Rochester.rr.com
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> On Behalf Of Monona Rossol
Sent: Thursday, August 13, 2020 4:51 PM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: Re: [DCHAS-L] Respirator physicals?
You can disagree, but there are those of us who think aerosols containing the virus can be between 0.3 and 1.0 microns. So out of caution, our recommendations for HVAC filters and masks all require efficiency at the typical 0.3 micron range. Monona
-----Original Message-----
From: Roger McClellan <roger.o.mcclellan**At_Symbol_Here**ATT.NET>
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Sent: Thu, Aug 13, 2020 3:45 pm
Subject: Re: [DCHAS-L] Respirator physicals?
To all:
An excellent article with straight forward methodology on protection afforded by masks was published in 2010 by a friend of mine-- Larry E. Bowen, Does that mask really protect you? Applied Biosafety , Volume 15. pp 67 -71 (2010) . Do not be concerned that he used a saline aerosol. The Mass Median Aerosol Diameter was 1.6 microns with a geometric standard distribution of 2.0. This is about what I would expect for a hospital rooom. Remeber the virus particles are likely a small fraction of the mass of most particles, other materials in the particles will dominate in determining particle size. Remember the atmosphere both in doors and out doors (ambient) is very dynamic with continuous movement and change in particles (including droplets) as particles agglomerate, hydrate, shrink as they dry, air movement, settle, etc.
In my opinion, the behavior in the atmosphere and deposition in the respiratory tract of "virus containing particles" is governed by the same physical, chemical and physiological properties and concepts that govern ALL particles. The particles are vectors for relatively small quantities of virus.
Roger O. McClellan
On Thursday, August 13, 2020, 01:16:35 PM MDT, Monona Rossol <0000030664c37427-dmarc-request**At_Symbol_Here**lists.princeton.edu> wrote:
This is the study that has cause major contention on other forums I inhabit. It seems like the clever use of a call phone camera and conversions from pixels to particle size are an anathema to many people technically grounded in this field. I personally find this such a creative idea that despite the probably built in counting errors, I'm thinking of legally adopting the 5 young (I assume) authors.
But there is absolutely not the least acceptance of this data on one of the other forums. I'd like some of you on CHAS who understand the math to take a look. And until you do, assuming that the masks are a placebo should be postponed.
it is also important to remember that the purpose of this study was to demonstrate an inexpensive way of evaluating masks. Masks are not their expertise and the researchers obviously just purchased 14 assorted masks and used them to demonstrate their method. The most glaring example of how little they know about masks is their identification of one of them as an N95 with an exhalation valve. Unless NIOSH is into shiny black as a fashion statement now, this is obviously not an N95.
So rather than use this as a study of masks, let's try to find out if there is any use for the method of testing masks and if it is accurate enough to be useful. Because if it is, your answer, like all your answers today, is in your phone.
Monona
-----Original Message-----
From: Margaret Rakas <mrakas**At_Symbol_Here**SMITH.EDU>
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Sent: Thu, Aug 13, 2020 1:46 pm
Subject: Re: [DCHAS-L] Respirator physicals?
I would just like to point out a new study by Duke researchers (especially for those who are concerned a surgical mask or cloth mask may not much be more than a placebo):
Wishing everyone a safe and healthy late summer-
Margaret
On Thu, Aug 13, 2020 at 6:02 AM Reinhardt, Peter <peter.reinhardt**At_Symbol_Here**yale.edu> wrote:
Lots more research is necessary, here. Aerosols appear to be an important means of COVID-19 transmission, however the evidence still points to large droplet spread as being the predominant means of transmission. (Fomite transmission contributes also, but in minor way.) Thus, in public areas, the six foot distancing rule is an every effective for reducing transmission and should be one of our key messages, along with mask-wearing, hand washing and not touching one's face.
Regarding aerosols and droplets, we still don't know how many virus particles will cause an infection, but it is likely that a droplet will contain more of them than a finer particle. Further, distance, space, dispersion will all generally result in a lower probably of an infectious dose landing on your mucus membranes. Your risk will always be higher when standing within six feet from an infectious person than if standing twenty feet away.
p.s.., Yale has 100,000 KN95 masks and we can't fit people to any of them.
p.s..s., We don't normally do spirometry as part of our respirator medical evaluations, unless the person's medical history indicates its necessity.
p.s..s.s., Re the "medical paper mask" comment, ASTM surgical masks used in hospitals are effective droplet protection and do provide some filtration. Years of evidence has proven their effectiveness in preventing disease in healthcare workers. See https://www.cebm.net/covid-19/what-is-the-efficacy-of-standard-face-masks-compared-to-respirator-masks-in-preventing-covid-type-respiratory-illnesses-in-primary-care-staff/ For infection control, these same masks are used in healthcare facility for "source control" (e.g., transporting a TB patient), which I agree is not PPE.
Pete Reinhardt, Yale EHS Director
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> on behalf of Monona Rossol <0000030664c37427-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU>
Reply-To: Monona Rossol <actsnyc**At_Symbol_Here**cs.com>
Date: Wednesday, August 12, 2020 at 8:39 PM
To: "DCHAS-L**At_Symbol_Here**Princeton.EDU" <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Subject: Re: [DCHAS-L] Respirator physicals?