title: An experimental study on effects of increased ventilation flow on students' perception of indoor environment in computer classrooms.
abstract: The effects of ventilation in computer classrooms were studied with university students (n = 355) in a blinded study, 31% were women and 3.8% had asthma. Two classrooms had a higher air exchange (4.1-5.2 ac/h); two others had a lower air exchange (2.3-2.6 ac/h). After 1 week, ventilation conditions were shifted. The students reported environmental perceptions during the last hour. Room temperature, RH, CO2, PM10 and ultra-fine particles were measured simultaneously. Mean CO2 was 1185 ppm at lower and 922 ppm at higher air exchange. Mean temperature was 23.2 degrees C at lower and 22.1 degrees C at higher air exchange. After mutual adjustment (temperature, RH, CO2, air exchange), measured temperature was associated with a perception of higher temperature (P < 0.001), lower air movement (P < 0.001), and poorer air quality (P < 0.001). Higher air exchange was associated with a perception of lower temperature (P < 0.001), higher air movement (P = 0.001), and better air quality (P < 0.001). In the longitudinal analysis (n = 83), increased air exchange caused a perception of lower temperature (P = 0.002), higher air movement (P < 0.001), better air quality (P = 0.001), and less odor (P = 0.02). In conclusion, computer classrooms have CO2 levels above 1000 ppm and temperatures above 22 degrees C. Increased ventilation from 7 l/s per person to 10-13 l/s per person can improve thermal comfort and air quality.
  
  
  CONCLUSIONS
  Computer classrooms are crowded indoor environments with a high thermal load from both students and computer equipment. It is important to control room temperature either by air conditioning, sun shields, or sufficiently high ventilation flow. A high ventilation flow is also crucial to achieving good perceived air quality. Personal ventilation flow should be at least 10 l/s. Possible loss of learning ability due to poor indoor air quality in university buildings deserves more attention.
authors.affiliation: Medical Science-Occupational and Environmental Medicine, and Department of Medical Science, University Hospital Uppsala, Uppsala, Sweden. dan.norback@medsci.uu.se
authors.forename: D
authors.initials: D
authors.lastname: Norbäck
authors.forename: K
authors.initials: K
authors.lastname: Nordström
mesh_terms: D000328:Adult; D000389:Air Conditioning; D016902:Air Pollution, Indoor / Q000032:analysis*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D010465:Perception; D016037:Single-Blind Method; D013334:Students / Q000523:psychology*; D011795:Surveys and Questionnaires; D013548:Sweden; D014495:Universities; D014691:Ventilation