By the Division for Air Quality

When Division for Air Quality educator Roberta Burnes works with students, she often starts with a single question: How do we know if the air is clean?

In other words, how do we know if the air is meeting federal air quality standards?

“Answering this question is tricky because you can’t see or smell many air pollutants,” said Burnes. And when she asks students whether air quality in Kentucky has gotten better or worse in the last fifty years, most of them say worse.  “Nothing could be farther from the truth,” she said.

So when Burnes visited a Frankfort home school group last month, she took the students on a virtual journey through time to see how far we’ve come in cleaning up our air. “Since the Clean Air Act was passed by Congress in 1970 and amended in 1990, air quality has improved dramatically,” said Burnes.  For example, power plant emissions of nitrogen oxides in Kentucky have dropped 76 percent since the year 2000, while sulfur dioxide emissions have fallen 86 percent.

But how do we know these things?

“The best way for students to understand how we know what we know about air quality,” said Burnes, “Is to provide them with the tools to discover that on their own.”  Her approach follows the Next Generation Science Standards (NGSS), which are educational standards that Kentucky adopted in 2015.  The NGSS requires students to demonstrate their understanding of science concepts by applying science and engineering practices to solve real world problems.

On the students’ work table, Burnes scattered a variety of household and craft materials including paper plates, cups, scissors, tape, cotton balls, coffee filters, nylon stockings and pipe cleaners. Their task?  Design and build a model instrument to collect and measure particulate matter in the air.

Over the next hour, students worked in teams to design and assemble their models. “It’s not as simple as you might think,” said Burnes. “Students had to solve a number of smaller challenges first: How do I draw air through the instrument?  How do I collect particulate matter?  How will I measure what I collect?”

Some students created elaborate filtration systems designed to separate larger particles from smaller ones. Others built model fans that would pull air through the filters.

“It’s amazing to see the creative solutions students come up with,” said Burnes. “Their models hit on many of the same principles that real air monitors use.”

Afterwards, each student team presented their model to the rest of the group, explaining how it worked and how they would measure the data it collected. “I had no idea that a class could be so fun, and at the same time you could learn so much”, said 10-year-old Sophie Dufour.  “Making models, seeing pictures, and doing activities, I learned what is really going on in our world.”

If you would like Division for Air Quality staff to visit your classroom, contact roberta.burnes@ky.gov.

A student uses a pipe cleaner “fan” to waft air inside the model sampler.

Students finish construction of the pollution collector.

Students use coffee filters for fan blades in their model.

Students work in teams to design and build model air samplers.

The student team describes how air will flow through the sampler system of filters.

This team creates a multi-layered filtration system to trap different sized particles.

Using everyday materials, students create models that capture many of the design features of real air samplers.

How Does a Real Air Sampler Work?

The Division for Air Quality utilizes a variety of air samplers and analyzers to monitor criteria pollutants across the Commonwealth. Every pollutant must be measured by a specific type of instrument, in a specific way.  Here is the science behind how it works for some of the most common pollutants:

Particulate Matter (PM_2.5): Just like the student projects mentioned above, real particulate matter samplers work by pulling a stream of air through a filter. By comparing the weight of the filter before and after sampling, the amount of particulate matter can be determined.

Sulfur Dioxide (SO₂): A sulfur dioxide analyzer shoots a beam of ultraviolet light through an air sample.  SO₂ molecules absorb a portion of this energy and then re-emit the energy at a characteristic wavelength of light.  The more SO₂, the more light energy emitted.  An instrument measures the light emitted and converts it to a parts per million measurement.

Nitrogen Dioxide (NO₂): This gaseous pollutant is difficult to measure directly.  Instead, the air sampler converts NO₂ into its molecular cousin, nitric oxide (NO).  Nitric oxide reacts with ozone, which is produced by a generator in the analyzer.  The analyzer is then able to calculate the amount of NO₂ in the original sample.

Ozone: Ozone absorbs ultraviolet light.  An ozone analyzer shoots a beam of ultra violet light through an air sample.  The amount of light absorbed by the sample indicates the level of ozone in that sample.

A close-up of an SO2 analyzer.

DAQ scientist Rebecca Graves works with several analyzers in the Division’s lab.

Ozone monitor inlet valve. Gaseous pollutants such as nitrogen dioxide, sulfur dioxide and ozone are measured by drawing air through an inlet valve into an analyzer.

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Photos by the Division for Air Quality.