Author Technology and Engineering Teacher - Volume 76, Issue 4 - December/January 2017
PublisherITEEA, Reston, VA
ReleasedNovember 15, 2016
Technology and Engineering Teacher - Volume 76, Issue 4 - December/January 2017

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SAFETY SPOTLIGHT: Overcrowding in K-12 STEM Classrooms and Labs

There is a statistically significant correlation between overcrowding and increased accident rates.



Overcrowding in science, technology, engineering, and mathematics (STEM) classrooms is the number one safety concern among STEM teachers (Horton, 1988; Macomber, 1961; Stephenson, West, Westerlund, & Nelson, 2003; West & Kennedy, 2014; West, Westerlund, Nyland, Nelson, & Stephenson, 2002). Indeed, there is a statistically significant correlation (p<0.001) between overcrowding and increased accident rates as seen in Figures 1 and 2 based on a study of 270 accidents (Stephenson et al., 2003; West & Kennedy, 2014). Overcrowding can occur in any type of room where STEM activities occur such as labs or classrooms or combination lab/classrooms or makerspaces.


Overcrowding Defined

While overcrowding has long been linked with accidents in all types of STEM rooms, it is more complex because overloading STEM classes manifests itself in three very different ways including occupancy load, class size, and the amount of workspace per student. Another factor that needs to be considered is the difference between a “combination classroom/laboratory or workspace” or “makerspace,” and a “pure laboratory or workspace” or “makerspace” where different activities occur in each area. Only hands-on laboratory investigations or activities occur in a “pure laboratory,” whereas in a combination classroom/laboratory, only non-lab instructional activities occur in the classroom area. This distinction is important when determining space limitations. States such as Texas, Massachusetts, Vermont, California, and Georgia have requirements that limit class sizes using different criteria such as their state facilities standards.


Occupancy Load: Overcrowding is defined and regulated by the National Fire Protection Association (NFPA) Lab Occupancy code. The STEM laboratory is considered a vocational subject area by NFPA. Fifty (50) square feet of net free space per person (not just students) is the amount of space required as per the provisions of the NFPA 101 Life Safety Code®. Note this regulation refers to a pure laboratory/room that is used only for hands-on STEM activities, not typical classroom activities such as lectures or group/individual activities. This regulation typically applies to the amount of space in the lab area of the combined type of room. This limitation is primarily a safe egress regulation in case of fire.


Class Size: Class sizes greater than 24 (in any one class) limits a teacher’s ability to supervise a large number of students doing STEM activities with hazardous chemicals, materials, tools, or equipment. Overcrowding in regard to supervision likely affects a teacher’s ability to properly manage and oversee his or her classroom, and therefore may prevent the adequate supervision of students conducting STEM activities. Interestingly, professional science teachers’ organizations have long recommended limiting science class sizes to 24 occupants if the room is of adequate size to accommodate the needed individual space. This reccommendation could be applied to technology and engineering education laboratories since they are also categorized as vocational subject areas by NFPA. Moreover, since technology and engineering education tends to use more hazardous equipment, it would seem judicious to use an even lower maximum class size than 24 students for those classes. A student/teacher ratio above the research findings and professional standards creates greater risk of accidents for students and their teachers. Accidents significantly (p<0.001) increase as the class size increases (Stephenson, 2003; West & Kennedy, 2014; West,, 2002) (Figure 1).


Workspace per student: A lack of individual workspace or “elbow room” per student is also linked to increased accident rates. As STEM students are working with hazardous chemicals (ACS, 2012), materials, tools, or equipment, adequate individual workspace is required to be able to move freely and work safely. Accidents significantly (p<0.001) increase as the amount of space per student decreases (Stephenson, 2003; West & Kennedy, 2014; West,, 2002) (Figure 2).



Work with your school and district administrators, local and state school boards, teacher and administrator organizations, and your local Fire Marshall to better understand the research, requirements, and professional standards to ensure that students and teachers are provided safer learning and working environments. For additional safety-related information, see the issue papers from the National Science Teachers Association (NSTA, 2016) and ITEEA’s comprehensive safety guide (DeLuca, Haynie, Love, & Roy, 2014). 



American Chemical Society (ACS). (2012). Guidelines and recommendations for the teaching of high school chemistry. Retrieved from 

DeLuca, V. W., Haynie, W. J., Love, T. S., & Roy, K. R. (2014). Designing safer learning environments for integrative STEM education (4th ed.). Reston, VA: ITEEA.

Horton, P. (1988). Class size and lab safety in Florida. Florida Science Teacher, 3(3), 4-6.

Macomber, R. D. (1961). Chemistry accidents in high school. Journal of Chemical Education, 38(7), 367-368.

National Science Teachers Association (NSTA). Safety in the Science Classroom. (2016). Safety issue papers by NSTA’s safety advisory board. Retrieved from

Stephenson, A. L., West, S. S., Westerlund, J. F., & Nelson, N. C. (2003). An analysis of incident/accident reports from the Texas science laboratory safety survey, 2001, School Science and Mathematics, 103(6), 293-303. doi:10.1111/j.1949-8594.2003.tb18152.x.

West, S., & Kennedy, L. (2014). Science safety in secondary Texas schools: A longitudinal study. Proceedings of the 2014 Hawaiian International Conference on Education, Honolulu, HI.

West, S. S., Westerlund, J. F. Nyland, C. K., Nelson, N.C., & Stephenson, A. L. (2002). What the safety research says to Texas science teachers. The Texas Science Teacher, 31(1), 11-15.



Sandra S. West, Ph.D., is an associate professor of Biology and Science Education at Texas State University and the Legislative Liaison for the Science Teachers Association of Texas. She also serves on the National Science Teachers Association (NSTA) Safety Advisory Board and the International Council of Associations for Science Education Safety Committee. She can be reached at


Have questions or a safety issue that you would like to see addressed in a future Safety Spotlight article? Please send them to Dr. Tyler Love at