Sick building syndrome in relation to air exchange rate, CO(2), room temperature and relative air humidity in university computer classrooms: an experimental study.
OBJECTIVE
To study the effects of ventilation and temperature changes in computer classrooms on symptoms in students.


METHODS
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 (CO(2)), PM10 and ultra-fine particles (UFP) were measured simultaneously (1 h). Illumination, air velocity, operative temperature, supply air temperature, formaldehyde, NO(2) and O(3) 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.


RESULTS
Totally 31% were females, 2.9% smokers and 3.8% had asthma. Mean CO(2) was 993 ppm (674-1,450 ppm), temperature 22.7 degrees C (20-25 degrees 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 microg/m(3) at lower and 15 microg/m(3) at higher ventilation flow. Ocular, nasal and throat symptoms, breathlessness, headache and tiredness were significantly more common at higher CO(2) and temperature. After mutual adjustment, ocular (OR = 1.52 per 1 degrees C), nasal (OR = 1.62 per 1 degrees C) and throat symptoms (OR = 1.53 per 1 degrees C), headache (OR = 1.51 per 1 degrees C) and tiredness (OR = 1.54 per 1 degrees C) were significantly associated with temperature; headache was associated only with CO(2) (OR = 1.19 per 100 ppm CO(2)). Longitudinal analysis demonstrated that increased room temperature was related to tiredness (P < 0.05).


CONCLUSIONS
Computer classrooms may have CO(2) above 1,000 ppm and temperatures above 22 degrees C. Increased temperature and CO(2) may affect mucosal membrane symptoms, headaches and tiredness. Room temperature was most important. CO(2) associations may partly be temperature effects.
Norbäck
Dan
D
Department of Medical Sciences, Occupational and Environmental Medicine, Uppsala University, University Hospital, Uppsala, Sweden. dan.norback@medsci.uu.se
Nordström
Klas
K
D000328:Adult; D016902:Air Pollution, Indoor / Q000009:adverse effects* / Q000032:analysis; D002245:Carbon Dioxide / Q000009:adverse effects* / Q000032:analysis; D003201:Computers; D018592:Cross-Over Studies; D005221:Fatigue / Q000453:epidemiology / Q000209:etiology; D005260:Female; D006801:Humans; D006813:Humidity; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis; D018877:Sick Building Syndrome / Q000453:epidemiology / Q000209:etiology*; D013334:Students; D013548:Sweden / Q000453:epidemiology; D013696:Temperature; D014495:Universities; D014691:Ventilation; D055815:Young Adult
D052638:Particulate Matter; D002245:Carbon Dioxide