Portable Schools#2 – Do they pose unique air quality and health issues compared to more traditional schools?

Portable classroom spaces are indeed different from traditional classrooms.  In a study conducted in California for the Air Resources Board, portable classrooms were twice as likely to have carpeted floors, slightly more likely to have pressed wood bookcases, 3-4 times more likely to have metal roofs, and more likely to have suspended ceilings.

            Pressed wood cabinetry is a concern as indicated in the previous posting as they are a potentially significant source of formaldehyde, a potent mucous membrane irritant.  Though such cabinets may be found in traditional classrooms, they are likely to be older and thus less potent formaldehyde sources. Levels above 50 ppbv are of concern.

            A move to carpeted floors has been occurring in schools for more than a decade.  Teachers favor them as they convey a sense of comfort and a degree of sound absorption.  The use of carpeting in classrooms is not particularly desirable as it serves as a reservoir for the accumulation of a wide variety of allergens (including pet dander, cockroach, mold ) that children and staff bring to school on their clothing.  Such allergens and other organic debris are difficult to remove from carpet and as such, pose an allergen exposure concern on re-suspension.  Studies at our university as well as in Europe indicate that pet allergens brought to school by children are often sufficient concentrations to cause symptoms in sensitized individuals.

            Roof leaks and subsequent wetting and mold infestation on ceiling tiles is a common problem in school buildings. Roof leaks were reported in 27% of all portables in California even though most portables have metal roofs. Combined with ceiling tile that suggests a potential for water damage and mold infestation.

            Most portable classroom spaces are heated/cooled by packaged wall-mounted heat pump units.  Because of perceived noise with such units, teachers tend to turn off the fans.  Such packaged units are problem-plagued.  They are difficult to adjust to provide for adequate outdoor air ventilation.

            In the California portable school study, carbon dioxide (CO₂) levels (a measure of ventilation adequacy) were reported to be similar in both portable and traditional classrooms with about 43% of classroom spaces above acceptable guideline values.  These results suggest that portable classroom spaces are just as poorly / adequately ventilated as the average traditional classroom.  Since portable classrooms are most commonly used as elementary classrooms than is the case for traditional school buildings CO₂ level comparisons may result in erroneous conclusions about the relative degree of ventilation provided. Since CO₂ emissions reflect body mass, elementary students produce less CO₂ than high school and middle school students.  As such CO₂ levels in elementary schools under the same ventilation conditions with older students will be considerably lower (half or more) .This likely poorer ventilation in portable schools is consistent with the fact that portable school teachers report more stuffiness than traditional school classroom teachers.   

October 3, 2003

 Indoor Environmental Quality (2000), Thad Godish Ph.D., C.I.H

Direct E-mail 00tjgodish@bsu.edu