Classroom aerosol dispersion: desk spacing and divider impacts

Abstract

A study of aerosol dispersion was conducted in a university classroom using a CO2 tracer gas emitted from three source locations in a steady release, one source location per test. The tracer gas emitted from the single source location represented the potentially infectious aerosol droplets emitted from a single student and was thus a way to examine the influence of one sick student on the rest of the class. Two parameters were adjusted during the testing—the spacing of the desks, which included a spread and compressed configuration, and the inclusion of three-sided clear dividers attached to the student desk surfaces. Tracer dispersion was measured through the use of monitors in 13 locations within the classroom, with eight monitors representing seated student locations, four monitors representing a standing instructor along the classroom front, and one monitor at the return vent in the ceiling. As expected, spacing strongly influenced concentration levels at desks adjacent to the source location. The use of dividers reduced overall student and instructor location tracer concentrations when compared to desks without dividers in most cases. Finally, the influence of air change differences on the results was noted with consistent trends. The experimental construct provides a systematic means for classroom testing that may be broadly applicable to various configurations of classrooms beyond the one tested. Graphic abstract

Classroom aerosol dispersion modeling: experimental assessment of a low-cost flow simulation tool

“…For classroom A in the high ow condition, both models predicted concentrations near the door and at the back of the room reasonably well, with models matching one another at monitors 3-5. However, STAR-CCM + matched observed concentrations much more closely in the front of the room (8)(9)(10)(11)(12). Neither model accurately predicted the low concentrations measured near the window (6 and 7), which was present in tests 2a and 2b.…”

“…Results between the models varied signicantly in parts of the room as well, with both modeling the results of test 1a better than test 1b. Overall, SolidWorks did a better job of predicting concentrations along the front of the room (7)(8)(9)(10)(11), which are the most likely locations for an instructor to stand in this particular room conguration.…”

“…Although this is time-and laborintensive, it can yield useful results for specic classroom conditions. [9][10][11][12][13][14][15] Such studies oen use aerosol particle generators or CO 2 tracer gas release in conjunction with an array of monitors throughout the room to investigate dispersion, or the effectiveness of air purier systems. However, the studies are limited because they cannot be quickly repeated to see the effects of changes to boundary conditions, such as ventilation conditions, source location, room geometry, or other factors.…”

Potential of physical barriers integrated with personal exhaust ventilation in decreasing airborne infection risk for people

“…However, previous studies have shown that physical barriers significantly impact direct airborne transmission more than indirect transmission [2]. Dacunto et al investigated the dispersion of aerosols in a university classroom by including three-sided clear dividers attached to student desk surfaces [3]. The use of partitions decreased overall contaminant concentrations in most cases when compared to desks without partitions.…”

Effects of location, classroom orientation, and air change rate on potential aerosol exposure: an experimental and computational study

“…Results were used to validate CFD modeling that quantified the benefit of the air cleaner under a variety of conditions, though results varied depending upon the location of the source. Dacunto, et al 26 released a CO 2 tracer gas in a classroom as a proxy for the smallest aerosol particles which would remain airborne for hours and follow the air streamlines. They found that desk spacing strongly influenced concentrations at desks adjacent to the source, and that the use of transparent barriers around desks reduced overall tracer concentrations at both student and instructor locations.…”