With growing concerns about pollution and its effects on health, air quality is an issue that affects everyone, yet most studies focus on outdoor air quality. Our team’s project sought to close the knowledge gap of what factors can contribute to worsening indoor air quality. Our study was conducted at various buildings at the University of San Diego (USD) where we explored whether indoor air is as clean as we think and how it compares to the air outside. Indoor air quality matters since it can lead to many health problems; here is a link to a study that explores indoor exposure to air pollutants (https://www.niehs.nih.gov/health/topics/agents/indoor-air).
We hypothesized that older buildings on campus would show worse levels of indoor air quality, especially near vents, and that outdoor air fluctuations would have a larger overall impact on indoor air quality than indoor factors. Understanding the sources of major air pollutants within various indoor environments can help direct attention to weak points in creating a clean breathing environment. Furthermore, understanding this can help us to potentially identify buildings that pose health risks and contribute to decisions about improving air systems in aging infrastructure.
To test our hypothesis, our team used Flow air quality sensors (Figure 1) to measure the air quality index of common pollutants, PM10 (particulate matter) and NO2 (nitrogen dioxide), inside various buildings on USD campus. In addition, proximity to air vents, entrances, floor level, and building age were observed for each data point; a fractional factorial method (Figure 2) was used to statistically analyze how different factors influenced the pollutant levels.
Figure 2. Fractional Factorial method setup.
Our data partially supported our initial hypothesis. While outdoor air quality (especially NO2) was worse when compared to indoor (Figure 3), it did not always depend on a building’s age. Instead factors such as a building’s floor level and outdoor conditions on the sampling day had a larger impact on the air quality indoors. This shows that while older buildings might contribute to poorer indoor air quality, outdoor pollution and meteorological factors also play a key role. In addition, when sampling outdoor air quality in proximity to cars our team observed an increase in NO2 pollution (Figure 4).
Figure 3. Indoor vs outdoor air quality for NO2 and PM10.
Figure 4. Proximity to cars for PM10 and NO2.
Though our findings provided valuable insights, more research is needed to fully understand how indoor air quality is affected by other variables, such as weather or the use of ventilation systems. Our fractional factorial method indicated some factors but with fairly low confidence. The higher the slope number shown in the Figure 5 the more influence that factor has on indoor air quality. How much can better building designs improve indoor air, especially in older structures? Further studies can help answer this question. By shedding light on these important issues, we hope our research will encourage the campus community to think about air quality inside the buildings they use daily and push for healthier, cleaner air environments across campus.
Figure 5. Fractional Factorial method results.