It should be stated that higher relative humidity values contribute to the survival and the dispersion of airborne allergens such as mould spores and bacteria, worsening the symptoms of allergy suffers.
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Carbon dioxide concentrations are often used as a surrogate of the rate of outside supply air per occupant. The indoor concentrations of CO 2 showed inadequate classroom air exchange rates. Figure 1 depicts the variation of indoor CO 2 concentrations in a typical working day at the three schools. A strong correlation of the CO 2 level with occupancy has been observed. CO 2 spikes were even more pronounced when students started physical activities inside the classrooms, as for example, art classes or entrance and exits to the playgrounds.
This room was the only one that had the electric wall heating constantly connected and windows and doors always closed. Lower outdoor air ventilation rates at homes have been associated with increased prevalence of asthma and allergic symptoms in children. No standards have been agreed upon for nitrogen oxides in indoor air in Portugal.
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NO 2 concentrations were higher outdoors than indoors Table 3 , probably as a result of vehicular exhaust emissions from nearby traffic. SJ School, which is located near an avenue with intense traffic, presented the smallest level of indoor NO 2 , possibly because the windows and the doors were always closed. In the School, fungal colony-forming units higher than this standard were observed in both indoor and outdoor air. The main factors affecting atmospheric dispersion and survival of microorganisms are the relative humidity, temperature, oxygen, wind and air turbulence, air pollutants and water and nutrient availability.
The high amounts of bacteria in both indoor and outdoor may derive from several factors, including high seasonal level of bioaerosols in outdoor air, from the human self-activities, such as breathing, sweating and movement causing particle resuspension. Cold weather favours children's respiratory infections, which are usually caused by bacteria or virus.
Thus, respiratory morbidity among children may also contribute to the airborne spread of bioaerosols. Scheff et al. Conversely, Godwin and Batterman 18 found that the outdoor bioaerosol levels exceeded indoor levels in 64 school classrooms in Michigan. Total VOC concentrations could give information about the influence of aerosol sprays, solvents, cleaning agents, pesticides, paints and repellents.
Figure 3 shows a daily profile for the total VOC concentrations. In the School, there was a huge increase in the VOC concentrations around 13 pm, when pupil's art class was occurring with the use of glue and paints. This makes evident that collage and painting materials increase the VOC levels in indoor air. Zhang et al. Table 4 present the results for the VOC concentrations and speciation. In general, concentrations of VOCs were higher indoors than outdoors for all schools.
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Those compounds that have only been detected in indoor air have a probable indoor source. Ethyl acetate, methyl acetate, styrene, ethanol and limonene were only found in the indoor air. Pollutants identified in both indoor and outdoor samples, but with higher concentrations in the indoor environments, may indicate additional indoor sources or inadequate ventilation ratios. Toluene concentrations were higher than those reported by Stranger et al. The high benzene and toluene concentrations observed in Lisbon are in the same range of those measured in schools of Oporto, Portugal.
SJ School, which has the oldest building among all institutions, registered both the highest concentrations and diversity of VOC compounds. Perhaps the inadequate ventilation observed favours accumulation of pollutants with additional indoor sources. Limonene could be derived from cleaning products, air fresheners and many other consumer products. Indoor and outdoor concentrations of NO 2 , VOCs, formaldehyde and microbiological components were measured for the first time in 3 elementary schools in Lisbon during December Low ventilation ratios and the children's physical activities have also an impact upon the CO 2 levels.
Most of the assessed gaseous pollutants can be credited to the traffic emissions and indoor sources some architectural finishes, floor adhesives, PVC flooring, consumer products and cleaning products. More studies are needed currently underway , to find additional possible sources of indoor contamination, to calculate air exchange rates on a seasonal basis, to evaluate if there is a causal relationship between pollutant exposure and health symptoms in schools, and to assess if school IAQ can adversely affect academic performance or attendance.
Pegas thanks FCT for the Ph. The authors would also like to thank the support of principals, staff and students at the three schools. In addition, an acknowledgement is addressed to Profs.
Cunha and A. Almeida University of Aveiro for their support in bioaerosol determinations. Blondeau, P. Khan, I.
Mendell, M. Public Health , 92 , Kim, J. May, K. Bhugwant, C.
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