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From: David EldrEdge <Dave.EldrEdge**At_Symbol_Here**NALTIC.COM>
Subject: Re: [DCHAS-L] DCHAS-L Digest - 30 Jul 2026 to 10 Aug 2026 (#2026-114)
Date: Aug 11, 2026 17:13 UTC
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
In-Reply-To: Re: [DCHAS-L] DCHAS-L Digest - 30 Jul 2026 to 10 Aug 2026 (#2026-114)
I agree with Joseph Sabol.
CO₂ sensors are great for checking ventilation when you have a steady source of CO₂ from living, breathing people, e.g., students.
Typical outdoor CO₂ is often around 450 to 550 ppm in more populated areas. If your indoor CO₂ climbs to 2000 ppm, or even as high as 6000 ppm or more, you know you have a ventilation problem that needs attention.
My teaching lab is about 450 m³ and has as many as 24 students plus myself. I keep an Aranet4 running during our lab sessions. Only once have I seen the CO₂ rise above 700 ppm, and that was when the fume hoods malfunctioned for about an hour.
Here is a calculator you can use to estimate ACH (air changes per hour) for a given space:
Visit: tinyurl.com/ACHcalc1
One reason I am particularly concerned about ventilation is the potential for respiratory aerosols to build up. I have pulmonary fibrosis and really cannot afford another hospital stay. I started monitoring ventilation at the beginning of the pandemic and completely avoided infection during that period even until today. Prior to the pandemic, I had pneumonia three years in a row, was hospitalized twice, and only this year finally got the related hospital bills resolved. My alarm bells start going off when I see CO₂ above about 800 ppm.
Toronto was one of the first library systems I remember seeing make CO₂ monitors available for patrons to borrow.
If you are on social media, try searching for #SchoolCO2. You will be led to a lot of fascinating real-world examples of CO₂ monitoring in classrooms and other occupied spaces.
CHAS,
My opinion:
Every room (school, public library, city hall, etc) should have a CO2 monitor proxy for fresh air (and temp and RH.) Inexpensive, my local library has units for loan.
Laboratories where "chemicals" are used? It depends. If methane burners, I recommend monitoring VOCs and NO2. Of course, anyplace with a flame should have a CO detector.
You should have a pretty good idea of the lab atmosphere. I hope this helps. Cheers!
Joseph Sabol, Ph.D.
CHEMICAL CONSULTANT
Providing chemical and business development services since 1999.
Racine, Wisconsin USA
https://chem-consult.com
> On 08/11/2026 12:00 AM EDT DCHAS-L automatic digest system <listserv**At_Symbol_Here**lists.princeton.edu> wrote:
>
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> There are 10 messages totaling 4444 lines in this issue.
>
> Topics of the day:
>
> 1. Gas Sensor (3)
> 2. Lab Vacuum Line Repair Questions.
> 3. CHAS 2026 Update: Accomplishments so far and What’s Ahead
> 4. NEW EPISODE OUT NOW: What Season 1 Taught Us About Learning and Systems
> 5. Laboratory signoff consulting opportunity in southern New Jersey
> 6. Assistance representing CHAS at our CHAS promotional table during the ACS
> 2026 Fall Meetings and Convention in Chicago Aug. 23rd - Aug. 26 (2)
> 7. Abstract Submission Is Now Open for ACS Spring 2027
>
> ---
> For more information about the DCHAS-L e-mail list, contact the Divisional membership chair at membership**At_Symbol_Here**dchas.org
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> ----------------------------------------------------------------------
>
> Date: Wed, 5 Aug 2026 21:18:54 +0000
> From: "Murphy, Dr. Ruth Ann" <rmurphy**At_Symbol_Here**UMHB.EDU>
> Subject: Gas Sensor
>
> Good Afternoon,
>
> Are gas sensors required in chemistry labs with natural gas utilities and/or liquid nitrogen use? If so, what type of sensor is needed? Thank you!
>
> Best,
>
> Ruth Ann Cook Murphy, PhD
> Professor of Chemistry
> University of Mary Hardin-Baylor
> 900 College Street
> Belton, TX 76513
> (254) 295-4542
>
>
>
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