From: John Callen <jbcallen**At_Symbol_Here**GMAIL.COM>
Subject: Re: [DCHAS-L] Face masks and solvents
Date: Thu, 25 Jun 2020 18:36:20 -0500
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID: E76F5B31-8317-49A3-8236-5BFD9A52B64F**At_Symbol_Here**


The cloth masks under consideration for COVID-19 are designed to help provide asepsis, a physical barrier between the wearer and his/her surroundings with other people.  

A surgical mask (FDA Class II) helps provide asepsis, a physical barrier between the wearer and her/his work environment or sterile field. 

They do not offer respiratory protection.  They are designed to trap on the inside particulate matter which may come from coughing, sneezing, talking or other mucous secretions, etc.

As it relates to solvent vapors, it is analogous to having a mesh screen door or a submarine.  Solvent vapors will go through synthetic or natural cloth masks and into the lungs of the wearer.  

Being "trapped on or in" cloth face masks is obviously dependent upon how much of the liquid solvent "splashed" onto the cloth mask and its rate of evaporation controlled by temperature, pressure, relative humidity and the normal or labored breathing of the wearer. 

I remember a situation many years ago when two chemical workers decided to do some solvent tank cleaning (non-confined space entry).  One wore one particle mask and the other wore three particle masks, thinking that he was "more protected."  Fortunately, the plant supervisor caught them and made them throw away the particle masks and get the Full Facepiece Respirators fitted with Organic Vapor Cartridges.

Be Safe & Well!

JohnB. Callen, Ph.D.
3M Personal Safety Division - Retired
ACS/DCHAS Founding Member
(312) 632-0195

a physical barrier between the wearer and the work environment or sterile field."
On Jun 25, 2020, at 5:37 PM, Jack Reidy <jreidy2**At_Symbol_Here**STANFORD.EDU> wrote:

I could have sworn this had come up already but after browsing through every DCHAS email since March 1st I couldn't find an answer. We have received several questions from labs about the risk of solvent vapors being "trapped" in cloth face masks. Some seem to be concerned that they will just be trapped in the breathing space, others are worried that they'll "stick" to the masks and desorb later. Here's what I've been thinking so far:
  • If there is sufficient vapor to cause concern, the work should be done in a fume hood.
  • If it's in a fume hood and there is still a sufficient quantity of solvent to cause health concerns, then there is either an issue with the fume hood or with how the user is operating, which should have become apparent in previous times without face masks.
  • The air in the cove should be largely the same as the room air; while these masks may stop certain sizes of solid particles or liquid droplets, gas exchange should not be inhibited. So, you're back to the first point: if the room's air is hazardous, you have a bigger problem than your mask.
  • As a side note to the above, I think similar logic can be applied to chemical compatibility/fire resistance questions. If a researcher is worried that a face covering could catch fire or react with something, then their bigger problem is that their face is on fire or has acid on it or something. Most of the clothing a researcher has is probably susceptible to fire or acids, but they still wear that into lab.
To be clear, not wearing a face covering is not an option. This isn't in our hands, our county government has mandated it and, to my understanding, is uninterested in making exceptions. Thanks in advance for the help/advice.
Jack Reidy (he/him)
Research Safety Specialist, Assistant Chemical Hygiene Officer
Environmental Health & Safety
Stanford University
484 Oak Road, Stanford, CA, 94305
Tel: (650) 497-7614
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