School IAQ: where children spend a third of their day

A typical school-aged child spends 35-40 hours a week inside school buildings, often more time than any single occupant spends in a typical office. The IAQ in those buildings ranges from excellent (newer construction with mechanical ventilation, MERV-13 filtration, monitored CO₂) to genuinely bad (1960s-1980s buildings with operable-window-only ventilation, deferred maintenance, and uncontrolled humidity). The EPA IAQ Tools for Schools program quantifies the problem and provides a framework; most US schools have not adopted it. See EPA Tools for Schools for the program details.

Classroom CO₂ is the headline. ASHRAE 62.1 specifies 10 cfm per person plus 0.12 cfm per square foot of outside air for K-12 classrooms; science laboratories retain 10 cfm per person with a higher 0.18 cfm per square foot area rate. The CO₂ that results at design occupancy varies with activity, outdoor CO₂, and air mixing rather than being fixed at 1,000 ppm. Harvard's Schools for Health report cites CO₂ at or below 1,000 ppm as the ventilation benchmark and notes that classrooms often exceed it: in one study of 120 Texas classrooms, time-averaged CO₂ was above 1,000 ppm in two-thirds of the rooms and peaked above 3,000 ppm in about one in five. The classroom-CO₂-and-learning literature connects these levels to measurable drops in attention, decision-making, and test performance.

Other problem spots in a school. Gymnasiums and locker rooms see VOC peaks from cleaning chemicals (gym mats, locker disinfectants) plus body-odor compounds plus PM₁₀ from synthetic-floor abrasion. Cafeterias add cooking PM_2.5 and NO_x if the kitchen ventilation undersizes the load. Older buildings (especially in humid climates or with flat roofs that have leaked) carry mold loads in walls and HVAC ductwork, see mold spores. School-bus diesel idling near the building intake is a documented PM and ultrafine-particle source; many districts now have anti-idling policies on paper that are routinely violated in practice. CDC Healthy Schools data underlines the children-specific stakes.

What works: MERV-13 filtration on supply air, portable HEPA in classrooms sized per CADR, a CO₂ monitor in each classroom with a 1,000 ppm threshold, a demand-controlled ventilation strategy that opens the outside-air damper when CO₂ rises (see DCV), and aggressive moisture management to prevent mold. The framework for advocating these is state IAQ-in-schools legislation (active in CT, NY, NJ, ME, and others), parent-teacher-association reporting, and direct conversations with district facilities staff. For acute events see school wildfire response; for the population side see children and air quality.