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PocketLab Air: Measuring Ozone

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Submitted by PocketLab on Mon, 05/06/2019 - 18:21

Background Information about Ozone

Ozone (O3) in our atmosphere is both good and bad. There is a helpful saying to remember is, “Ozone: good up high, bad nearby.” The “good” ozone is ozone high in our atmosphere that is part of the ozone layer. The ozone layer protects us from the sun’s ultraviolet rays. “Bad” ozone is ozone that occurs at ground level, where it can be inhaled. Ground level ozone is a pollutant and creates smog. 

Ground level ozone is not directly emitted. It is the result of sunlight causing a chemical reaction between nitrogen oxide (NOx) and volatile organic compounds (VOC). NOx and VOCs are emitted directly from sources like chemical plants, refineries, and cars. Ground level ozone can cause a variety of health problems and can weaken plants and ecosystems. 

Ozone Formation
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 ozone, as well as particulate matter (PM1, PM2.5, PM10), carbon dioxide, weather conditions, and can calculate the Air Quality Index. Using your phone's GPS, you can also map your data using your geo-location. 

PocketLab Air

How Does the Ozone Sensor Work?

The ozone sensor measures ozone concentration through an electrochemical reaction. Typical electrochemical sensors are large industrial sensors that use a liquid electrolyte. The PocketLab Air uses a new type of sensor with a solid state electrolyte to enable PocketLab to be small and portable. The electrochemical ozone sensor operates through the following method:

  • Ozone in the air passes through a filter to screen out particles and moisture.
  • The ozone molecules undergo a chemical reaction with the sensing electrode that generates free electrons.
  • The electrons flow through a conductive medium to the counter electrode.
  • The flow of electrons creates an electric current that is proportional to the concentration of ozone gas.
  • The electrodes are connected to a circuit to measure and amplify the current signal.

O3 Sensor Diagram

Lab Investigation

The PocketLab Air ozone measurements are strictly for educational purposes and should not be used for safety monitoring.

Ozone is a harmful gas to humans even in small amounts. Typical levels of ozone in the environment are at concentrations less than 50 parts per billion or 0.000005% of the molecules in the air. Unhealthy levels of ozone begin above 165 ppb concentration for an exposure time of one hour. 

We do not recommend trying to generate ozone gas for experiments without appropriate training and in a controlled laboratory environment. Unintentional sources of ozone generation can come from electric arcing or sparking in electric motors. Industrial ozone generators are commonly used to deodorize air and to disinfect water.

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

Citizen Science Investigation

When is your community most sensitive to ozone pollution? Measure ozone levels and weather conditions on a variety of days and in a number of locations. Some things to consider: 

  • Sunny days compared to cloudy days (use with light intensity data).
  • Warm days compared to cold days (use with temperature data).
  • Near known pollutant sources like highways and factories (use with geo location data).
  • Windy days compared to calm days (wind can carry ozone pollution to areas far away). 
O3 Sensor Diagram

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