title: Carbon dioxide (CO2) demand-controlled ventilation in university computer classrooms and possible effects on headache, fatigue and perceived indoor environment: an intervention study.
abstract: OBJECTIVE
  To study the effects of a CO(2) demand-controlled ventilation system (variable flow) in computer classrooms on perceived air quality and sick building syndrome.
  
  
  METHODS
  University students (27% women) participated in a blinded study. Two classrooms had variable flow (mean 5.56 ac/h); two others had constant ventilation flow (mean 5.07 ac/h). After one week, ventilation conditions were shifted. The students reported symptoms/perceptions during the last hour on rating scales. Temperature, air humidity, CO(2), PM10 and number concentration of particles were measured simultaneously. Cat (Fel d 1), dog (Can f 1), horse (Equ cx) and house dust mites (Der f 1 and Der p 1) allergens were measured in dust. Those participating twice in the same classroom (N = 61) were analysed longitudinally.
  
  
  RESULTS
  Mean CO(2) was 784 ppm (9% of time >1,000 ppm) with variable flow and 809 ppm with constant flow conditions (25% of time >1,000 ppm). Mean temperature (22.6 °C), PM10 (18 μg/m(3)) and number concentration (1,860 pt/cm(3)) were unchanged. The median levels of cat, dog, horse and Der f 1 allergens were 10,400 ng/g, 4,900 ng/g, 13,700 U/ng and 260 ng/g dust, respectively. There were slightly less headache (p = 0.003), tiredness (p = 0.007) and improved perceived air quality (p = 0.02) with variable flow.
  
  
  CONCLUSIONS
  Use of a CO(2)-controlled ventilation system, reducing elevated levels of CO(2), may slightly reduce headache and tiredness and improve perceived air quality. The high levels of pet allergens, due to track in of allergens from the home and possible accumulation due to electrostatic forces, illustrate a need for improved cleaning.
authors.affiliation: Department of Medical Science, Occupational and Environmental Medicine, University Hospital, Uppsala University, 751 85 Uppsala, Sweden. dan.norback@medsci.uu.se
authors.forename: Dan
authors.initials: D
authors.lastname: Norbäck
authors.forename: Klas
authors.initials: K
authors.lastname: Nordström
authors.forename: Zhuohui
authors.initials: Z
authors.lastname: Zhao
mesh_terms: D000328:Adult; D016902:Air Pollution, Indoor / Q000009:adverse effects* / Q000032:analysis; D000485:Allergens / Q000032:analysis; D000818:Animals; D002245:Carbon Dioxide / Q000009:adverse effects* / Q000032:analysis; D002415:Cats; D018592:Cross-Over Studies; D004285:Dogs; D004391:Dust / Q000032:analysis; D005221:Fatigue / Q000139:chemically induced; D005260:Female; D006261:Headache / Q000139:chemically induced; D006736:Horses; D006801:Humans; D006813:Humidity; D008297:Male; D010465:Perception; D039981:Pyroglyphidae; D018877:Sick Building Syndrome / Q000139:chemically induced*; D016037:Single-Blind Method; D013696:Temperature; D014495:Universities; D014691:Ventilation / Q000379:methods*; D055815:Young Adult
chemical_list: D000485:Allergens; D004391:Dust; D002245:Carbon Dioxide