In this study, we investigated the indoor air quality (IAQ) in classrooms with exhaustventilation systems and in naturally ventilated classrooms. In the latter, we found peak CO2-concentrations of more than 4000 ppm. 1500 ppm was exceeded during 40 to 86% ofteaching time, dependent on class size. The windows were opened rarely in winter which ledto low mean air exchange rates of 0.20 0.23 h^-1. The operation of mechanical ventilationsystems improved IAQ considerably. Peak CO2-concentrations decreased to less than 2500ppm. 1500 ppm was exceeded for only 7 to 57% of teaching time.
Some techniques aimed at the evaluation of microclimatic parameters through the measurement of other indoor physical quantities are critically reviewed. Particularly, the appraisal of the air velocity from the predicted mean vote and the determination of air change from the decay of the C02 indoor concentration are analysed. Important warnings for the use of these methods are underlined and the limits of applicability are pointed out.
Describes a method for determining the air change rate in a room or a building by continuous monotoring of the CO concentration in both supply and exhaust air. By using a mass balance equation, the indoor concentration of CO can be numerically calculated for various air change rates. The value of the air change rate used in the equation that gives the best correlation between measured concentration and calculated concentration provides an estimate of the air change rate for the volume studied.
Describes how carbon dioxide is metabolically produced and can therefore be associated with the presence of occupants. Also it is relatively easy and inexpensive to measure, and it is fairly stable. In principle CO2 can be used to evaluate the ventilation rate, determine the proportion of outdoor air that is blended with recirculated air and provide an indication of perceived indoor air quality.
The UK government has signed the Kyoto Protocol and it has committed to reducing C02 emissions to 20% below 1990 levels by 2010. As buildings are responsible for approximately half of the UK C02 emissions, of which the domestic sector accounts for 50%, meeting this target will require a significant contribution from the domestic sector.
Five classrooms, air-conditioned or naturally ventilated, at five different schools were chosen for comparison of indoorand outdoor air quality. Temperature, relative humidity (RH), carbon dioxide (C02), sulphur dioxide (S02), nitric oxide (NO), nitrogen dioxide (N02), particulate matter with diameter less than 10 μm (PM10), formaldehyde (HCHO), and total bacteria counts were monitored at indoor and outdoor locations simultaneously. Respirable particulate matter was found to be the worst among parameters measured in this study.
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