Abstract
Nanoparticles (NPs) can infiltrate indoor environments and have a large impact on human health when inhaled. Thus, indoor air quality is highly dependent on the outdoor air and on the filters used in the ventilation systems. In the NanoOffice study, the concentrations and the size distribution of NPs were measured with a five-minute time resolution in twelve office buildings in Umeå. Measurements were taken with an SMPS 3938 during a one-week period in the heating and nonheating seasons. Large differences in ventilation between buildings appeared, despite the fact that similar MVHR ventilation systems were used, and most of them were equipped with F7 filters. The NP concentrations and the simultaneous ventilation flows were measured in buildings with a variable and a more constant ventilation flow. In some cases, an increase in NP concentration could be seen after ventilation turn-on or after an increase in the ventilation flow. There was also one case where the NP concentrations increased in connection with the ventilation being switched off or reducing its flow. However, variable NP concentrations were also shown in buildings with a fairly constant ventilation flow, which was prominent for the two buildings located closest to busy streets. The correlation coefficients between the ventilation flow and particles in different size classes were in general smallest for particles in the smallest size classes, indicating higher filtration efficiency.
Highlights
Nanoparticles are important to address due to their very small size and high penetration rate [1]
This study showed that the I/O ratios of particles in the different size fractions were weakly but positively correlated with the amount of ventilation provided to the indoor environment
Nanoparticles were measured in twelve office buildings during two oneweek periods representing daytime and nighttime during both the heating and nonheating season
Summary
Nanoparticles are important to address due to their very small size and high penetration rate [1]. A nanoparticle is defined as a submicroscopic particle that measures less than 100 nanometers (nm) on at least one of its dimensions [2]. The term is used for larger particles up to 500 nm [3,4]. There are several sources of nanoparticles originating both indoors and outdoors. Indoor sources of nanoparticles include electrical appliances [5], the release from several types of construction materials [6], and emissions from laser printers [7]. Outdoor air is an important source of nanoparticles, where the particles enter the buildings through infiltration or ventilation [8]
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