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The South Coast Air Quality Management District evaluates the performance of low cost sensors in the field and laboratory. These sensors have good correlation to federal refence methods for their cost. They offered me the best value for the money. Below are links to sensor evaluations for both types, particle and gas. You can compare field and lab results.
Siting your sensors:
Siting your sensors:
Install them away from HVAC and obscure spaces that prevent the flow of freely moving air. The Purple Air sensor is weather resistant, but the Aeroqual ozone sensor needs shelter from rain and snow. You will also need electricity.
If you can, place your sensors near your classroom for easy access. You want to ensure no one touches the sensors by accident or out of curiosity. The sensors can do little harm to students left alone, but students can do a good deal of harm to the sensors.
Unlike water quality monitoring or gardening, air quality sensors are not as exciting and directly hands-on. The data collection takes place remotely in a black box. Students view the data in a spreadsheet to graph and analyze. However, if you are looking for ways to collect authentic data in a virtual classroom, then this is an excellent way to teach scientific thinking and practices. There is some up front set up for the teacher, but the rest can easily be shared with students online.
Price, Quality, and Other Considerations
Price, Quality, and Other Considerations
Ozone sensors
Gas sensors, can read as low as parts per billion; cost ranges from $200 to $10,000
Correlation to Federal Reference Methods varies, 0 to 1.0
Aeroqual S-500 is an indoor device so must be sheltered outside and needs electricity
Outside when logging only; store in box when not used
Sensitive to VOC’s
PM sensors
Particle counters convert into micrograms per cubic meter; cost ranges from $100 to $7,000
Correlation to Federal Reference Methods varies, 0 to 0.94
PA-II is WIFI or PA-II is both WIFI and micro SD card/outdoor 24-7
Purple Air map displays data from wifi; must get permission to connect to your organization's wifi
Some things you can do with the sensors
Some things you can do with the sensors
Students collect ozone data, graph and analyze it. Here is an image of four days of ozone collected by a school in NoVA. You can see the diurnal pattern clearly.
Students collect ozone data, graph and analyze it. Here is an image of four days of ozone collected by a school in NoVA. You can see the diurnal pattern clearly.
A student is observing the diurnal pattern and making a prediction about ozone changes over the next several days.
A student is observing the diurnal pattern and making a prediction about ozone changes over the next several days.
This is a graph of PM 2.5 data from September 9 to 16, 2019. Notice the higher weekend PM 2.5 peaks on the 14th and 15th. This data is from a sensor in the District of Columbia. This school is near a highway, Metro commuter rail, coal carrying freight trains, and busy streets with traffic.
This is a graph of PM 2.5 data from September 9 to 16, 2019. Notice the higher weekend PM 2.5 peaks on the 14th and 15th. This data is from a sensor in the District of Columbia. This school is near a highway, Metro commuter rail, coal carrying freight trains, and busy streets with traffic.
This is also a graph of PM 2.5 data from September 9 to 16, 2019. Notice the lower weekend PM 2.5 peaks on the 14th and 15th. This data is from a sensor in the Northern Virginia suburbs of District of Columbia. There is a bus stop near the sensor and a busy county road nearby.
This is also a graph of PM 2.5 data from September 9 to 16, 2019. Notice the lower weekend PM 2.5 peaks on the 14th and 15th. This data is from a sensor in the Northern Virginia suburbs of District of Columbia. There is a bus stop near the sensor and a busy county road nearby.
This student is installing his school's Purple Air sensor.
This student is installing his school's Purple Air sensor.
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