The study, titled Association Between Classrooms CO2 Concentrations and Student Attendance in Washington and Idaho, found that a 1,000 ppm increase in carbon dioxide was associated with a 0.5 to 0.9 percent decrease in annual average daily attendance. That corresponded to a relative 10 to 20 percent increase in student absence.
Although the researchers cautioned against drawing general conclusions from the study, they say the results should serve as motivation for larger school studies to investigate associations of student attendance, and occupant health and student performance, with carbon dioxide concentrations.
If the study’s finding’s are confirmed, the researchers wrote, improving classroom ventilation should be considered a practical means of reducing student absence. Adequate or enhanced ventilation may be achieved, for example, with educational training programs for teachers and facilities staff on ventilation system operation and maintenance.
Also, technological interventions such as improved automated control systems could provide continuous ventilation during occupied times, regardless of occupant thermal comfort demands.
The study collected data from 409 traditional and 25 portable classrooms from 22 schools located in six school districts in Washington and Idaho. Researchers found that attendance at portable classrooms was 2 percent lower than that found in traditional classrooms.
Study classrooms had individual heating, ventilation, and air conditioning systems, except two classrooms without mechanical ventilation. Classroom attributes, student attendance and school-level ethnicity, gender, and socioeconomic status were included in multivariate modeling. Forty-five percent of classrooms studied had short-term indoor carbon dioxide concentrations above 1000 ppm.
Because of the small sample of portable classrooms in the study, researchers cautioned against drawing conclusions before larger studies can be conducted. They did, however, point to recent evidence in Los Angeles County that suggested relatively higher indoor air concentrations of toxic and odorous volatile organic compounds are possible in portable classrooms, as are higher occupant densities. In addition, it is not known whether inferior IEQ could cause such a large increase in absence.
Researchers addressed how improving student attendance would impact funding. In many school districts, funding is linked to annual average daily attendance. For example, in California the most currently available (2001 –2002) funding rate is $12.08 per student-day not absent. For a classroom of 20 children with a 185-day school year, a 1 percent decrease in annual average daily attendance, or 20 percent relative increase in absence, is $450 per classroom in funding lost to the school district.
Research was conducted by D.G.Shendell, D.Faulkner, W.J.Fisk and M.G.Apte all of Lawrence Berkeley National Laboratory,Environmental Energy Technologies Division; R.Prill of Washington State University Cooperative Extension Energy Program; amd D.Blake Northwest Air Pollution Authority.
