Ultrafine and Fine Particulate Matter Inside and Outside of Mechanically Ventilated Buildings

Abstract

The objectives of this study were to measure levels of particulate matter (PM) in mechanically ventilated buildings and to improve understanding of filtration requirements to reduce exposure. With the use of an Ultra High Sensitivity Aerosol Spectrometer and an Aerodyne Mass Spectrometer, ultrafine (0.055–0.1 μm) and fine (0.1–0.7 μm) indoor and outdoor PM was measured as a function of time in an office, a university building, and two elementary schools. Indoor particle levels were highly correlated with outdoor levels. Indoor and outdoor number concentrations in Denver were higher than those in Boulder, with the highest number concentrations occurring during summer and fall. The ratio of indoor-to-outdoor (I/O) PM was weakly but positively correlated with the amount of ventilation provided to the indoor environment, did not vary much with particle size (ranged between 0.48 and 0.63 for the entire size range), and was similar for each period of the week (weekend vs. weekday, night vs. day). Regression analyses showed that ultrafine indoor PM baseline concentrations were higher at night from nighttime infiltration. A lag time was observed between outdoor and indoor measurements. Weekday days had the shortest lag time of 11 min, and weekend nighttime lags when the HVAC was not in use were 50 to 148 min. Indoor-outdoor PM concentration plots showed ultrafine PM was more correlated compared to fine, and especially when the HVAC system was on. Finally, AMS data showed that most of the PM was organic, with occasional nitrate events occurring outdoors. During nitrate events, there were less indoor particles detected, indicating a loss of particulate phase nitrate. The results from this study show that improved filtration is warranted in mechanically ventilated buildings, particularly for ultrafine particles, and that nighttime infiltration is significant depending on the building design.

Sensors and Analytical Technologies for Air Quality: Particulate Matters and Bioaerosols

“…[20] Accurate evaluation of the distribution of ultrafine particulate matter in air is of utmost significance to public health, especially for children. [21,22] However, the detection of FPs and UFPs posed major challenges as the commonly used PM 2.5 index fails to provide size distribution for FPs and UFPs. Benefitting from the advancement of nanotechnology, Yu et al, demonstrated a size spectrometer by using a nanofiber array for probing FPs and UFPs with an unprecedented size resolution of 10 nm ( Figure 7).…”

Genotoxic effects of daily personal exposure to particle mass and number concentrations on buccal cells

“…This is probably due to higher particle generation in places where the volunteers carried out activities for this occupation category, most of the time in the center of the city, where there is an intense flow of vehicles. Additionally, fine particles are transported and accumulated inside workplaces, and thus increasing the level of exposure (Wu et al, 2012;Miller et al, 2017). The 'transport' presented the largest mass concentrations in larger sizes, probably associated with the resuspension material from auto-related activity.…”

Investigation of outdoor air pollutant, PM2.5 affecting the indoor air quality in a high-rise building

“…Airborne particles in buildings come from the outdoors through the building envelope with infiltrating air or the ventilation system's leakages. [7][8][9][10][11][12] Two existing strategies have been widely used to control IAQ in buildings: installing a high-efficiency air filter system 10,[13][14][15] and increasing the ventilation rate. 10,13,[16][17][18][19][20] In mechanically ventilated buildings, the outdoor particles, which infiltrate through gaps in the building's envelope with the infiltration air, could directly impact IAQ.…”