Student attendance in American public schools is a critical factor in securing limited
operational funding. Student and teacher attendance influence academic performance.
Limited data exist on indoor air and environmental quality (IEQ) in schools, and how
IEQ affects attendance, health, or performance. This study explored the association
of student absence with measures of indoor minus outdoor carbon dioxide concentration
(dCO(2)). Absence and dCO(2) data were collected from 409 traditional and 25 portable
classrooms from 22 schools located in six school districts in the states of Washington
and Idaho. Study classrooms had individual heating, ventilation, and air conditioning
(HVAC) systems, except two classrooms without mechanical ventilation. Classroom attributes,
student attendance and school-level ethnicity, gender, and socioeconomic status (SES)
were included in multivariate modeling. Forty-five percent of classrooms studied had
short-term indoor CO(2) concentrations above 1000 p.p.m. A 1000 p.p.m. increase in
dCO(2) was associated (P < 0.05) with a 0.5-0.9% decrease in annual average daily
attendance (ADA), corresponding to a relative 10-20% increase in student absence.
Annual ADA was 2% higher (P < 0.0001) in traditional than in portable classrooms.
This study provides motivation for larger school studies to investigate associations
of student attendance, and occupant health and student performance, with longer term
indoor minus outdoor CO(2) concentrations and more accurately measured ventilation
rates. If our findings are confirmed, 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.