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PocketLab Air: Measuring Particulate Matter

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Submitted by PocketLab on Mon, 05/06/2019 - 17:41

Background Information on Particulate Matter

Particulate matter consists of small particles suspended in the atmosphere. Dust, pollen, sea salt, soil particles, mold, soot, smoke, and other fine substances create a mixture of particulate matter that we inhale with every breath. According to the EPA, particulate matter greater than 10 micrometers is generally filtered away in our nose and throat. Particulates less than 10 micrometers can often pass into the lungs. The smaller the particle size, the farther it can move into the cardiovascular system and cause serious health concerns. 

Inhalable coarse particles (PM 10)

Diameter: 2.5 micrometers - 10 micrometers
Emission sources: fossil fuel combustion, dust from construction and other industrial sites, larger particles from wildfires and brush burning, and pollen 

Fine Particles (PM 2.5 and PM 1.0)

Diameter: 2.5 micrometers and smaller
Emission sources: fossil fuel combustion (gasoline, oil, diesel fuel), particles in smoke from wildfires, particles formed when pollutants from industries and cars react in the atmosphere.

Particulate Matter Diagram
Image from the U.S. EPA

PocketLab Air

PocketLab Air is an all-in-one science lab for investigating climate change and air pollution in your environment. PocketLab Air can measure particulate matter (PM1, PM2.5, PM10) as well as carbon dioxide, ozone, weather conditions, and can calulcate the Air Quality Index. Using your phone's GPS, you can also map your data using your geo-location. 

PL Air

How Does the Particulate Matter Sensor Work?

The PM sensor uses the principle of laser scattering to count the particles in the air. The PM sensor operates through the following method:

  • A laser diode shines a light beam through a cavity.
  • A fan draws air into the cavity with fine dust particles suspended in the air.
  • As the laser beam shines through the air, the dust particles deflect or scatter some of the laser light.
  • A light sensor, called a photodiode, measures how much laser light is transmitted through the cavity and how much is scattered by the dust particles.
  • The microprocessor in the sensor converts the light measurements into dust concentration measurements, using a process called Mie scattering theory (named after German physicist Gustav Mie).

PM Sensor Diagram


Lab Investigation

You can generate and measure changes in PM concentration to better understand how the PM sensor works and responds to environmental conditions. Example activities:

  1. Burn a match, candle, or incense near the PocketLab Air and observe changes in the measurement. Try blowing out the candle or match and see what happens.
  2. Record data in your kitchen before, during, and after you cook something on the stove. What happens when you start a strip of bacon sizzling?!

For more environmental science lessons, using PocketLab Air, click here. 


Citizen Science Investigation 

No Idling Zones: There are many places in neighborhoods were automobiles sit while their engines idle. Examples where idling vehicles could be unhealthy for nearby people:

  1. School buses and parents in their cars during pick-up and drop-off time at school
  2. City busses at a transit station
  3. Dump trucks and other equipment at a construction site

Set up your PocketLab Air to record PM 10, PM 2.5, and PM 1.0 data during times when the vehicles are idling and in the same location when there are no idling vehicles. What do you notice? Can you find evidence to support more “No Idling Zones” in your community?

PM Sensor Diagram

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