From:
Neufelder, Teresa M <000022237b09be0b-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU>
Subject:
Re: [DCHAS-L] Optimal Number of Students per TA/Instructor in General Chemistry Labs
Date:
Aug 25, 2025 20:57 UTC
Reply-To:
ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID:
<DM4PR10MB75089F96694C71C1AA445E81EE3EA**At_Symbol_Here**DM4PR10MB7508.namprd10.prod.outlook.com>
In-Reply-To:
<SN6PR01MB49275434BEAAF769F4E9D8BFEE3EA**At_Symbol_Here**SN6PR01MB4927.prod.exchangelabs.com>
Dear Patricia,
I work at a small 2-year college with maximum of 24 students in a lab designed for 24 students which does not allow for more students to be added to the lab as part of school safety policy in Chemical Hygiene Plan. I do not leave my lab unattended unless
all chemicals are put away and students are just working on post lab questions.
I do not believe a traveling TA or instructor is safe. There should be one supervisor per laboratory space/room. Make this a policy in your Chemical Hygiene Plan as run through your safety committee to get more internal backing prior to going to admin. You
can also get data to support carbon dioxide build up in spaces that do not have fume hoods. There are literally maximum number of students in a classroom based on this data.
Hope this helps,
Teresa Neufelder
Chemistry Instructor
South Central College
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> on behalf of Leach, Patricia <Patricia.Leach**At_Symbol_Here**UTDALLAS.EDU>
Sent: Monday, August 25, 2025 2:00 PM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Subject: [DCHAS-L] Optimal Number of Students per TA/Instructor in General Chemistry Labs
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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

SLC 3.513
Office: 972-883-6583
Cell: 469-891-6426
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