Indoor air quality in day-care centers, kindergartens, and primary schools: a pediatric health-oriented operational framework aligned with European and U.S. IAQ standards.

Authors

Carmen Díaz-López, Alejandro Morales-Ruiz, María Dolores Joyanes-Díaz, Carmen M Muñoz-González

Published in

Frontiers in pediatrics. Volume 14. Pages 1801649. Epub Jun 16, 2026.

Abstract

Children aged 0-12 spend many hours in day-care and school buildings characterized by high occupant density, synchronized occupancy peaks, intense activity, and frequent transitions. Exposure patterns differ between early childhood settings (day care/kindergarten/preschool) and primary schools due to differences in schedules, floor-level activity, cleaning routines, and staff-mediated operations. However, recent evidence remains heterogeneous and is often interpreted without sufficient differentiation between educational levels or adequate emphasis on operational verification under real-world conditions.
This study aims to (O1) synthesize recent in situ evidence on IAQ in day-care, kindergarten/preschool, and primary school settings; (O2) identify determinants explaining exposure patterns (D1, occupancy/use intensity; D2, ventilation strategy and real operation; D3, seasonality and comfort-driven rebound; D4, outdoor pollution context, D5 envelope-moisture pathway); and (O3) translate the evidence into a conceptual, verifiable N1-N3 pathway aligned with European and U.S. normative anchors.
PRISMA 2020 reporting was followed. Searches in Scopus, Web of Science, and PubMed (2018-2025; last search conducted on 12 September 2025) identified 990 records (Scopus, 345; Web of Science, 456; PubMed, 189). After removing 289 duplicates, 701 records were screened, and 614 were excluded based on title and abstract. Reports assessed for eligibility (n = 87) led to the exclusion of 61 studies with documented reasons, leaving 26 studies included in the qualitative synthesis. Data were managed in Excel with audit fields and standardized operational metrics (in-occupancy P90, percentage of time out of range, exceedance duration, pollutant peaks, and humidity risk-time indicators). Educational level, ventilation regime, season, and urban/outdoor context were explicitly coded. For ease of traceability, study characteristics are reported in the main text.
Recurrent CO₂ exceedances were common when ventilation depended on occupant behavior, particularly in winter, when thermal comfort constraints limited window opening. Across the included studies and recent school-based correlation literature, CO₂ emerged as a robust indicator of occupancy-linked ventilation performance; however, it is not as a standalone surrogate for outdoor-dominated pollutants such as NO₂ or for all PM/VOC behaviors. Early childhood settings showed a stronger dependence on staff-mediated routines, cleaning schedules, and floor-level activity, whereas primary classrooms exhibited clearer accumulation during teaching blocks and greater room-to-room variability driven by timetables and teacher practices. Evidence on moisture, condensation, and mold was more limited and methodologically less standardized than the CO₂/ventilation evidence base; therefore, related recommendations are framed as precautionary and escalation-oriented rather than as equally validated across all contexts.
The manuscript's specific contribution is to reinterpret 26 recent in situ studies through an IAQ-centered, determinant-based lens that explicitly differentiates educational levels and translates heterogeneous findings into a conceptual, verifiable N1-N3 pathway. The review indicates that pediatric-relevant IAQ management should combine ventilation, filtration, source control, and moisture-risk mitigation and that performance should be verified using in-occupancy, episode-sensitive metrics rather than daily averages alone. The N1-N3 structure is presented as evidence-based implementation guidance derived from the review corpus and normative cross-checking; however, it requires further validation in applied school settings.

PMID:
42395610
Bibliographic data and abstract were imported from PubMed on 03 Jul 2026.

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