2022 Yes https://www.mdpi.com/1660-4601/19/8/4580 Isa, Khairul Nizam Mohd Asia Epidemiology Study Students Middle/Jr High (6-8) Carbon Dioxide (CO2) Particulate Matter (PM) Temperature Humidity Fungi Respiratory symptoms Feno School children Urban suburban indoor pollutants We found that the median of FeNO in the school children from urban areas (22.0 ppb, IQR = 32.0) were slightly higher as compared to the suburban group (19.5 ppb, IQR = 24.0). After adjustment of potential confounders, the two-level hierarchical multiple logistic regression models showed that the concentrations of PM2.5 were significantly associated with elevated of FeNO (>20 ppb) in school children from suburban (OR = 1.42, 95% CI = 1.17-1.72) and urban (OR = 1.30, 95% CI = 1.10-1.91) areas. Despite the concentrations of NO2 being below the local and international recommendation guidelines, NO2 was found to be significantly associated with the elevated FeNO levels among school children from suburban areas (OR = 1.11, 95% CI = 1.06-1.17). The findings of this study support the evidence of indoor pollutants in the school micro-environment associated with FeNO levels among school children from suburban and urban areas.