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Subject: Re: [DCHAS-L] cloth face masks
Date: Thursday, June 4, 2020 at 7:32:14 PM
Author: Monona Rossol <0000030664c37427-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU> 		Next by Date:
Subject: Re: [DCHAS-L] cloth face masks
Date: Fri, 5 Jun 2020 00:06:23 +0000
Author: Monona Rossol

From: Monona Rossol <0000030664c37427-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU>
Subject: Re: [DCHAS-L] cloth face masks
Date: Thu, 4 Jun 2020 23:35:53 +0000
Reply-To: Monona Rossol <actsnyc**At_Symbol_Here**cs.com>
Message-ID: 2029803383.3256030.1591313753514**At_Symbol_Here**mail.yahoo.com
In-Reply-To <689BDE6B-5490-4462-A79C-18F0055170AB**At_Symbol_Here**ilpi.com>


The route of the problem is recommending equipment based on availability rather than effectiveness.  In the richest country in the world, this whole thing shouldn't be.  but the studies from various countries show a practical relationship between everyone wearing masks and the numbers of cases coming down.  Monona


-----Original Message-----
From: ILPI Support <info**At_Symbol_Here**ILPI.COM>
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Sent: Thu, Jun 4, 2020 5:28 pm
Subject: Re: [DCHAS-L] cloth face masks

Sorta kinda.  Exhalation is a complex issue for which I have not seen a quantitative or authoritative study.  

An exhalation valve will still cut down on the largest droplets because they are going to impact the inside of the mask rather than make a ninety degree turn and go out the valve.  Although you can argue whether subsequent breaths will vaporize some of that.

However, ANY filtering facepiece mask, valve or not, has a positive internal pressure on exhalation.  With a non-valved mask (and even a valved one), some fraction of your outgoing breath is going to be filtered, but in all realistic probability, it's leaking out around the edges, probably significantly, particularly on a forceful exhalation.  I think it's easy to lull ourselves into the false sense of security that a simple mask will filter on exhalation but my guess is that at this point the rating really means nothing because the rating is for INhalation.  But still better than nothing or a non-tight (inhalation) seal.

Regardless, the CDC recommends a surgical mask over a valved respirator in situations where a surgical mask would normally be required to preserve a sterile field: https://www.cdc.gov/niosh/npptl/topics/respirators/factsheets/respsars.html#E

Of course, surgical masks are an even more false sense of security - while they stop droplets coming straight in or out, they leak around the edges REALLY bad. Same reference, different paragraph: https://www.cdc.gov/niosh/npptl/topics/respirators/factsheets/respsars.html#H

Even a good PAPR (powered air purifying respirator that provides a positive pressure of HEPA-filtered air to the wearer) is still not filtering the exhalation; just making it take a longer path where hopefully stuff drops out.  But the wearer is sitting pretty, for sure.

So caveats upon caveats.  At times it feels like we are making this all up as we go along.  Almost forgot: face coverings have two purposes, BTW - protect others AND protect the wearer.

We have a beautiful new N95 design arriving in August, BTW.  Been wearing the prototype and it's the most comfortable one I've used.  I'll post details on it when we get the official literature on it.

Rob Toreki

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On Jun 4, 2020, at 4:12 PM, Debbie M. Decker <00001204b93f9a5e-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU> wrote:

Excellent pragmatic advice.  Thanks, Zack.
 
One caveat - an N95 with an exhalation valve defeats the purpose of the face covering which is to prevent droplets from contacting others.
 
 
Debbie M. Decker, CCHO, ACS Fellow
Past Chair, Division of Chemical Health and Safety
Councilor and Programming Co-Chair
University of California, Davis
(530)754-7964
(530)304-6728
dmdecker**At_Symbol_Here**ucdavis.edu
 
Birkett's hypothesis: "Any chemical reaction
that proceeds smoothly under normal conditions,
can proceed violently in the presence of an idiot."
 
 
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On Behalf Of Zack Mansdorf
Sent: Thursday, June 4, 2020 12:07 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: Re: [DCHAS-L] cloth face masks
 
This has become an incredible circular discussion that I believe will be never ending.
 
If you are doing lab work that requires a respirator, use the correct respirator.  If you are doing lab work that does not require a respirator (e.g., in a hood), then use common sense..  If a face covering is more of a risk than not wearing a face covering (e.g., flammability, corrosivity, vision, etc.) than do not use a face covering and just maintain a 6 foot separation from other persons.  If you cannot and the face covering will not work, use a face shield.  Before my colleague and friend, Monna, admonishes me--..if you have access to an N-95 or better, use that.  It has become pretty clear that the vast majority of cases are from person to person contact and the likelihood of a younger person suffering severe consequences is very small.  Consider the overall risk of wearing a face covering versus not wearing a face covering given the lab work.  I do not think there is a universal solution for all circumstances nor a universal material that can be used in all circumstances.
 
That's my non-CDC sanctioned opinion. 
 
Zack
S.Z. Mansdorf, PhD, CIH, CSP, QEP
Consultant in EHS and Sustainability
7184 Via Palomar
Boca Raton, FL  33433
561-212-7288
 
 
 
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On Behalf Of Patricia Redden
Sent: Thursday, June 4, 2020 2:13 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: [DCHAS-L] cloth face masks
 
CDC is recommending the use of cloth face mask in academic institutions, but the question is what is the best fabric for them.  Lab coats in academic labs are supposed to be chemical- and fire-resistant.  Does this apply to face masks as well?  If so, is there a source for them?
 
Patricia Redden, Ph.D.
Professor, Chemistry Department
Fellow, American Chemical Society
Fellow, ACS Division of Chemical Health and Safety
 
SAINT PETER'S UNIVERSITY
The Jesuit University of New Jersey
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www.saintpeters.edu
 Named #1 in the nation for transformation in 2018 by the American Council on Education/Fidelity Investments  
 
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