Collecting Air Quality Data with PurpleAir

Collecting Air Quality Data with PurpleAir

Today’s post is by Christine Favilla!

Through SIUE’s STEM Center and the Department of Environmental Sciences, I am placing air quality sensors in local neighborhoods to look at the air quality of the region. Air quality is directly related to our health as well as the health of all Earth’s plants and animals. It is important to learn about your community’s air quality, what local industries and businesses put into the air, and how air quality can impact the health of people who live in our communities. By learning more about your community’s air quality, you can know when to stay indoors on days when the air quality is poor. These are the locations and areas where people plan to host air quality sensors:

  • Alton, IL
  • East Alton, IL
  • Edwardsville, IL
  • Fairmont/Collinsville, IL
  • Ferguson, MO
  • Granite City, IL
  • Highland, IL
  • Madison, IL
  • Mitchell, IL
  • SIUE East St. Louis Campus, IL
  • SIUE Edwardsville Campus, IL
  • Staunton, IL
  • St. Louis, MO

There are many chemicals in our air that can affect us in different ways. In fact, there are six Criteria air pollutants that have to be regulated in the United States. They all have National Ambient Air Quality Standards (NAAQS) that limit how much pollutants companies/industries can put into our air:

  • Particulate Matter (PM10 and PM2.5)
  • Sulfur Oxides (SOX, main one is SO2)
  • Carbon Monoxide (CO)
  • Nitrogen Oxides (NO, NO2)
  • Ozone (O3)
  • Lead (Pb)

The air monitors that we are placing in local neighborhoods measure particulate matter (PM). Particulate matter describes solid particles, including dust, smoke, and other organic and inorganic particles, suspended in air. We are using PurpleAir sensors that use two separate laser particle counters to count particle numbers by particle sizes of 0.3, 0.5, 1, 2.5, 5 and 10 μm and use count data to calculate PM1.0, PM2.5, and PM10 mass concentrations. Having two separate laser particle counters ensures that the instruments are precise: in science, precision is important because it shows that the measurements of each instrument represents what is actually happening in the environment. One way we can check precision is to see if measurements from one instrument matches those of another instrument. When we see matching data, we can feel more confident that we are getting good data.

The PurpleAir laser counter uses a fan to pull an air sample through a laser beam. Some particles in the air will reflect some laser light onto a detection plate. The reflection is measured as a pulse by the detection plate and the length of the pulse determines the size of the particle and the number of pulses determines the particle count. From these particle counts the mass concentrations of PM1.0, PM2.5, and PM10 are measured.

PurpleAir uses the Air Quality Index (AQI) established by the United States Environmental Protection Agency (EPA). This means that you can view the EPA’s AQI color coded safety graph on the PurpleAir Map for each of our PurpleAir sites. The color shows the PM2.5 reading in real time so we know what the air quality is for that day and time. Try clicking on a sensor icon on the PurpleAir map to see what the average data of the last 10 minutes for each laser counter is. It’s interesting to look at the ones in your neighborhood and compare it to ones in Las Vegas or even China that are all monitoring at the same time! Take a look for yourself here!

The SIUE monitors have not been placed and turned on just yet, but will be live in the next two weeks. We will make a post when they are up, so be sure to check the map then!