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Subject: Re: [DCHAS-L] Service Dogs in Teaching Laboratory

Date: Aug 27, 2025 22:37 UTC

Author: Alex Hagen <fischera**At_Symbol_Here**UW.EDU>

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Subject: Re: [DCHAS-L] Optimal Number of Students per TA/Instructor in General Chemistry Labs

Date: Aug 28, 2025 05:00 UTC

Author: James Caras <jamie**At_Symbol_Here**CATALYSTEDU.COM>

From: CRAIG MERLIC <merlic**At_Symbol_Here**G.UCLA.EDU>

Subject: Re: [DCHAS-L] Optimal Number of Students per TA/Instructor in General Chemistry Labs

Date: Aug 28, 2025 00:37 UTC

Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>

Message-ID: <SA1PR03MB7075559EC5142D01F1B735B7F13BA**At_Symbol_Here**SA1PR03MB7075.namprd03.prod.outlook.com>

In-Reply-To: <c3282d49-5762-4c80-83ae-fb2f4364802a**At_Symbol_Here**well.com>

Demystify: 
No matter what the ratio is, it is most important for the TA/instructor to be moving around the lab to see what students are doing while also answering questions and giving advice. They can never see what all students are doing at all times. In addition, a freshman lab should have minimal hazards and risks.  
The group consensus on this email thread is clearly ~24 students per TA/instructor. Patricia’s prior ratio of 15:1 is remarkable.  The new ratio of 76:3 or 25:1 might be acceptable if there are minimal hazards and risks and if the 3 TA/instructor are constantly moving around to monitor the students. 
A lab with only 20 students, but the TA standing in one spot would be less safe.




From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> on behalf of davivid <davivid**At_Symbol_Here**WELL.COM>
Sent: Tuesday, August 26, 2025 12:27:20 PM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Subject: Re: [DCHAS-L] Optimal Number of Students per TA/Instructor in General Chemistry Labs
 
What's the maximum if the TA sits out in the hall grading papers?
I've seen this at my former institution.

Dave Lane
CSO
Zyviva Labs

On 8/26/25 8:06 AM, Samuella Sigmann wrote:
> 1 TA/instructor to 24 students is the accepted best practice.
>
> There is no way that one person can safely monitor intro students in two
> adjoining laboratory rooms.
> Sammye
>
>
> On 8/25/2025 3:00 PM, Leach, Patricia wrote:
>>
>> Hello all,
>>
>> We have had an explosion in the number of freshmen who are taking
>> general chemistry this term, but funding has limited the number of TAs
>> and instructors we have per lab room. The way the department has had
>> to deal with this is to increase the number of students from 30 to 38
>> per section (limited by the Fire Marshall’s maximum occupancy of the
>> rooms). They work in groups of 3 (not ideal at all). We have adjoining
>> labs, so our shortage of instructors has been solved by having an
>> instructor supervise two sections being held concurrently in a set of
>> those labs. There is one TA per section.
>>
>> In the past we have had 30 students (10 groups) supervised by a
>> dedicated instructor (not working concurrent sections) and a TA, so
>> about 15 students per person supervising. Now we can have as many as
>> 38 students (13 groups) being supervised by one person at times, as
>> the instructor moves between sections. I feel this is not safe.
>>
>> What do people think is a safe ratio of supervising people to students
>> (or student groups)?
>>
>> Thanks,
>>
>> Patricia Leach
>>
>> Lab Manager
>>
>> Department of Chemistry & Biochemistry
>>
>> The University of Texas at Dallas <https://www.utdallas.edu/>
>>
>> SLC 3.513
>>
>> Office: 972-883-6583
>>
>> Cell: 469-891-6426
>>
>> --- For more information about the DCHAS-L e-mail list, contact the
>> Divisional membership chair at membership**At_Symbol_Here**dchas.org
>
> --
>
> ******************************************************************************
>
> Samuella B. Sigmann, MS, NRCC-CHO
>
> ACS Committee on Chemical Safety
> <https://www.acs.org/content/acs/en/about/governance/committees/chemical-safety.html>, Chair 2022-2024
>
> ACS Fellow, 2023
>
> ACS Division of Chemical Health & Safety <https://dchas.org/>_, _Fellow
> & 2019 Chair,__
>
> Appalachian State University, Retired
>
> Phone: 336 877 5147
>
> Email: sigmannsb**At_Symbol_Here**retired.appstate.edu
> <mailto:sigmannsb**At_Symbol_Here**retired.appstate.edu>__
>
>
> --- For more information about the DCHAS-L e-mail list, contact the
> Divisional membership chair at membership**At_Symbol_Here**dchas.org
> <mailto:membership**At_Symbol_Here**dchas.org>

---
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