Sick building syndrome in relation to air exchange rate, CO2, room temperature and relative air humidity in university computer classrooms: an experimental study



To study the effects of ventilation and temperature changes in computer classrooms on symptoms in students.


Technical university students participated in a blinded study. Two classrooms had higher air exchange (4.1–5.2 ac/h); two others had lower (2.3–2.6 ac/h) air exchange. After 1 week, ventilation conditions were interchanged between the rooms. The students reported symptoms during the last hour, on a seven-step rating scale. Room temperature, relative air humidity (RH) carbon dioxide (CO2), PM10 and ultra-fine particles (UFP) were measured simultaneously (1 h). Illumination, air velocity, operative temperature, supply air temperature, formaldehyde, NO2 and O3 were measured. Multiple logistic regression was applied in cross-sectional analysis of the first answer (N = 355). Those participating twice (N = 121) were analysed longitudinally.


Totally 31% were females, 2.9% smokers and 3.8% had asthma. Mean CO2 was 993 ppm (674–1,450 ppm), temperature 22.7°C (20–25°C) and RH 24% (19–35%). Lower and higher air exchange rates corresponded to a personal outdoor airflow of 7 l/s*p and 10–13 L/s*P, respectively. Mean PM10 was 20 μg/m3 at lower and 15 μg/m3 at higher ventilation flow. Ocular, nasal and throat symptoms, breathlessness, headache and tiredness were significantly more common at higher CO2 and temperature. After mutual adjustment, ocular (OR = 1.52 per 1°C), nasal (OR = 1.62 per 1°C) and throat symptoms (OR = 1.53 per 1°C), headache (OR = 1.51 per 1°C) and tiredness (OR = 1.54 per 1°C) were significantly associated with temperature; headache was associated only with CO2 (OR = 1.19 per 100 ppm CO2). Longitudinal analysis demonstrated that increased room temperature was related to tiredness (P < 0.05).


Computer classrooms may have CO2 above 1,000 ppm and temperatures above 22°C. Increased temperature and CO2 may affect mucosal membrane symptoms, headaches and tiredness. Room temperature was most important. CO2 associations may partly be temperature effects.

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This study was partly supported by grants from the Swedish Council for Worklife Research and the Swedish Foundation for Health Care Sciences and Allergy Research.

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Correspondence to Dan Norbäck.

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Norbäck, D., Nordström, K. Sick building syndrome in relation to air exchange rate, CO2, room temperature and relative air humidity in university computer classrooms: an experimental study. Int Arch Occup Environ Health 82, 21–30 (2008).

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  • Indoor air quality
  • Ventilation
  • Room temperature
  • Sick building syndrome (SBS)
  • University students