Carbon dioxide (CO2) demand-controlled ventilation in university computer classrooms and possible effects on headache, fatigue and perceived indoor environment: an intervention study
To study the effects of a CO2 demand-controlled ventilation system (variable flow) in computer classrooms on perceived air quality and sick building syndrome.
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, CO2, 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.
Mean CO2 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/m3) and number concentration (1,860 pt/cm3) 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.
Use of a CO2-controlled ventilation system, reducing elevated levels of CO2, 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.
KeywordsFurry pet allergens Indoor air quality Ventilation Room temperature Sick building syndrome (SBS) University students
- Almqvist C, Wickman M, Perfetti L, Berglind N, Renström A, Hedren M, Larsson K, Hedlin G, Malmberg P (2001) Worsening of asthma in children allergic to cats, after indirect exposure to cat at school. Am J Respir Crit Care Med 163:694–698Google Scholar
- Lindgren T, Norbäck D, Andersson K (2006) Perception of the cockpit environment among pilots on commercial aircraft. Aviat Space Environ Med 77:832–837Google Scholar
- National Swedish Board of Occupational Safety and Health (2000) The design of the workplace AFS 2000; 42 (in Swedish)Google Scholar
- Roth KW, Dieckmann J, Brodrick J (2003) Demand control ventilation. ASHRAE Journal, July 2003: 91–92Google Scholar
- Schell M, Inthout D (2001) Demand control ventilation using CO2. ASHRAE Journal, February 2001:1–6Google Scholar
- Smedje G, Norbäck D (2001) Incidence of asthma diagnosis and self-reported allergy in relation to the school environment-a four-year follow-up study in schoolchildren. Int J Tubercl Lung Dis 5:1059–1066Google Scholar
- Wargocki P, Sundell J, Bischof W, Brundrett G, Fanger PO, Gyntelberg F, Hanssen SO, Harrison P, Pickering A, Seppänen O, Wouters P (2002) Ventilation and health in non-industrial indoor environments: report from a European multidisciplinary scientific consensus meeting (EUROVENT). Indoor Air 12:113–128CrossRefGoogle Scholar
- World Health Organization (WHO) (2005) WHO air quality guidelines global update. WHO, Geneva (http://www.who.int/bookorders)