From: John Callen <jbcallen**At_Symbol_Here**GMAIL.COM>
Subject: Re: [DCHAS-L] Issues with face coverings
Date: Wed, 16 Sep 2020 23:47:18 -0500
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID: 704B8812-B06C-42A8-BA41-C534E03033A8**At_Symbol_Here**
In-Reply-To <271CF374-5079-4C09-B8ED-8AD6234E8ED6**At_Symbol_Here**>


Thank you and Monona for answering Kim's question and I agree that facial coverings should not to pose any concern about Kim's researchers' ability to smell.

There are two exceptions, which are both highly unlikely.

(1) The facial covering has a nose clip or equivalent which when pinched very hard, instead of being properly molded to the nose and face, totally blocks off and closes the nostrils; and,

(2) The facial covering is treated with activated carbon or certain other chemical sorbents you would find in respirator chemical cartridges.

Monona brings up the example of Hydrogen Sulfide (rotten egg smell) and that is a special case.  I'm sure you have heard the old saying, "If you can smell Hydrogen Sulfide, you are alive and if you can't smell it you will be dead.!  That's because Hydrogen Sulfide and certain other gaseous chemicals cause olfactory fatigue and loss of smell.  Hydrogen Sulfide has an odor threshold of 0.008 ppm - 0.13 ppm, current OEL, TWA = 1 ppm & STEL = 5 ppm and IDHL = 300 ppm (olfactory fatigue).

In thinking about this from a chemist's point of view: 

Kim, have your researchers had any experience during their formative education and training in chemistry labs where they use Whatman Filter Filters or Fritted Disk Funnels to separate solids from liquids in their experiments?

Just let them know that the Whatman filter or fritted disk behaves very much the same way as their facial coverings.

Or, to put it in the context of the home kitchen, washing fruit or vegetables in a colander, just as I did with my blueberries, tomatoes and romaine lettuce for my dinner tonight.

In summary, the facial covering behaves very much like the filter paper or fritted disk or colander; solids stay in/are trapped and liquids including gases and vapors move out.

Be Safe, Secure & Sound in Judgement, Vigilant as Always and Stay Well!

All My Best,

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


On Sep 16, 2020, at 8:54 PM, ILPI Support <info**At_Symbol_Here**ILPI.COM> wrote:

Nothing authoritative here, just logic and common chemical sense:

Odors are the individual molecules that reach your odor receptors (think about that next time you're cleaning the cat box!). Gaseous single molecules (vapors) are orders of magnitude too small to filter with fabric and will be unaffected by even an N100 face covering except perhaps for a de minimus amount of physisorption.

Aerosols containing odorants will be blocked by a properly fitted face mask because those particles are larger than the pores in the fabric. For example, you shouldn't smell Febreze or air freshener if someone sprays that while you're wearing a mask, at least initially until the aerosol carrier evaporates.

This is the whole basis by which masks prevent the transmission of SARS2 - while the virus particles are smaller than 0.3 microns, the aerosol particles they are riding on are approximately that size or larger and are greatly reduced or stopped by a properly fitted N95/N99/N100 mask.

As the researchers are in a lab and are more likely working with chemical vapors rather than aerosols, I would strongly doubt that simple masks pose any safety hazard with respect to odor detection.  I'm sure John Callen, who worked for 3M's Personal Safety Division and is the DCHAS resident guru on such, can add some insight here.

Of course, if we are talking about a mask with a charcoal or chemical absorbing cartridge or layer, then that's a different matter.

Rob Toreki

Safety Emporium - Lab & Safety Supplies featuring brand names
you know and trust.  Visit us at
esales**At_Symbol_Here**  or toll-free: (866) 326-5412
Fax: (856) 553-6154, PO Box 1003, Blackwood, NJ 08012

On Sep 16, 2020, at 7:55 PM, Kim Jeskie <jeskiekb**At_Symbol_Here**COMCAST.NET> wrote:

Just a curiosity question.  We have a research group raising concerns that face coverings could inhibit one's ability to smell, a sense they believe they really need to have in a laboratory setting. I've seen publications disputing concerns around carbon dioxide entrapment and heard plenty of practical comments about being able to smell cologne through the coverings, but I haven't seen anything published on this topic.  It sounds like a weak argument to me, but I don't want to simply discount this concern without a good faith effort to find out if there's any real evidence that this is a valid concern. Any thoughts/comments that you would care to share?


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