Air quality sensor network.
Emory Air Quality (Emory AQ) is an effort to monitor and report air quality around Emory University’s Main Campus. The high levels of development and traffic in and around Emory University raised the question “how clean is the air we breathe?” For this reason, Emory AQ currently monitors particulate matter (PM), temperature, and relative humidity.
Particulate MAtter (PM)
Particulate Matter (PM) consists of small particles and liquid droplets suspended in the air. Their chemical properties are determined by the composition of these solid and liquid particles. We measure PM using a Dylos sensor which divides PM into two categories: 2.5 to 10 micrometers in diameter(PM10), and 2.5 micrometers or smaller in diameter(PM2.5). The national standard for PM2.5 is 12 micrograms per meter cubed and for PM10 is 35 micrograms per meter cubed.
The Dylos particle counter doesn't take into account relative humidity when measuring the PM. This is a problem because if humidity is high, water will attach to particles and cause the particles to become larger. Thus the Dylos measures the particle as bigger than it actually is.
A good write-up of how humidity affects PM can be found here, a paper on research done in China can be found here, and information from the EPA on PM2.5 formation and relative humidity can be found here.
Environmental Health & concerns
PM, when inhaled, possesses a risk of aggravating or causing cardiorespiratory problems: asthma, lung and heart disease, difficulty breathing, and irritation. The smaller the particle, the deeper it can penetrate your lungs, or even your blood stream. For this reason, PM2.5 poses a greater health risk than PM10, pollen, or other large dust particles. Environmentally, the chemical composition of PM can contribute to chemical weathering, crop damage, and alter the pH of aquatic ecosystems. The EPA provides more information here.
Reporting air quality
The Environmental Protection Agency (EPA) establishes a National Ambient Air Quality Standard (NAAQS) for five major air pollutants (ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide), regulated by the Clean Air Act. These standards are used to establish the U.S Air Quality Index (AQI), a reporting index that categorizes the air into six degrees of health concern. For , the AQI criteria for “Good”, satisfactory air with little or no risk, is 12.0 micrograms per meter cubed. Anything beyond this threshold introduces risk to sensitive groups, such as those with asthma, as air quality decreases further.
Air Quality 101
Watch the educational video to see an Emory University student researcher, teach about air quality! View more videos like this on our Youtube channel.
In March 2021, a few of the Air Emory team led an event alongside the Atlanta Science Festival. The event was a small "air quality scavenger hunt" and it required participants to use a handheld air quality sensor and take readings at different, secret, locations around Old Fourth Ward Park. The event was designed to give those without much experience in air quality testing and general knowledge in air quality a look into our world. To further this outreach, we decided it would be fun to give people the chance to make their own at home air quality sensors, exactly like the ones we used at the event.
Below is documentation of the components used and their arrangement for the sensors we used during the 2021 Atlanta Science Festival. A small computer, called an Arduino, was used to process data collected by the laser particle sensor. This data was then displayed on a small LCD display.
Our Low Cost Sensor Set-Up Guide