I woke up on Sunday March 19 to the smell of burning wood. That’s nice, I thought, sleepily recalling the crackling fireplace in my childhood home. And then I remembered that my current house doesn’t have a fireplace. In fact, no one in our neighborhood has a wood fireplace.

The smoke was from a wildfire that was burning dangerously close to residential areas in Boulder, Colorado. More than 400 homes were evacuated. People living in over 800 other homes were told to prepare to evacuate in case the fire grew. (My home was much father from the fire.)

Walking our dog Mila that morning, Adam and I could see the smoke billowing up from the hills on the west side of Boulder. Adam took the photo below at about 9:40 AM from the park next to Crestview Elementary School in Boulder where Mila enjoys rolling in the grass no matter what natural disaster is afoot.

The smoke from the wildfire was visible from North Boulder on the morning of March 19.
Credit: Adam Holloway

Thanks to quick work by firefighters and planes dropping fire retardant, the fire was 50% contained by the end of the day, and totally under control by Monday.

A couple of days after the wildfire was extinguished and life returned to normal, Sharon Clark, a programmer at the UCAR Center for Science Education, was finishing up an interactive touchscreen slated for installation in a new air quality exhibit at the National Center for Atmospheric Research (NCAR) in Boulder. The touchscreen allows visitors to peruse data about local levels of two air pollutants: ground level ozone and particulate matter. At the time, Sharon was making sure the data was being fed into the screen for visitors to see when she pulled up the graph of particulate matter and saw a spike in particulates on March 19, during the fire.

Chart of particulate matter in Boulder, Colorado, showing a dramatic spike on March 19, 2017, during the Sunshine Fire .

The week of particulate matter data that Sharon Clark found while testing the screen for the air quality exhibit at NCAR. Note the spike in particulate matter associated with the wildfire. This is the smallest type of particulate matter (PM2.5). The EPA considers dangerous levels of PM2.5 to be more than 30 micrograms/m3 over a 24 hours period. This spike is over 80 micrograms/m3.
Credit: L.S. Gardiner/UCAR (graph), CDPHE (data)

It’s not good when a wildfire threatens people’s lives and homes, but it’s great to find the event recorded in the data. It helped us confirm that the sensor was recording particulate matter and that it was connected correctly to the screen in the exhibit. After months of creating an exhibit about the importance of keeping air quality good, here was evidence of air pollution in our backyard.

Villains in the Air: Particulate matter comic strip

Particulates are a combination of liquid droplets and solid specks in the air. Some are so small that they are invisible. Others are as large as a piece of dust. The smaller a particulate is, the longer it can stay in the atmosphere before falling to the ground. Very small particulate matter can get lodged deep within lungs. Exposure to high levels of particulates increases risk of respiratory disease, cardiovascular disease, and lung cancer.

According to U.S. National Ambient Air Quality Standards, healthy air has less than 35 micrograms of the smallest particulates per cubic meter of air over a 24 hour period. (The standard is averaged over 24 hours because instruments used to provide data over longer time periods.) The spike in particulate matter during the fire, about 80 micrograms per cubic meter of air, didn’t last very long, but it's still not healthy to breathe. We do not breathe air averaged over 24 hours. When smoke is in the air, consider staying indoors and reducing the amount you exercise outdoors.

According to Christine Wiedinmyer, a former NCAR scientist who studies what fires release into the atmosphere, particulate matter is just one of many emissions from wildfires. Fires also send nitrogen oxides, volatile organic compounds, and a lot of carbon dioxide into the air.

The air quality exhibit at NCAR was developed by the UCAR Center for Science Education in collaboration with the Regional Air Quality Council and several NCAR scientists who research air pollutants. If you are planning your visit to NCAR, be sure to check out the air quality exhibit!

The Sunshine Fire west of Boulder, Colorado, on the morning of March 19, 2017. Read more about the wildfire, known as the Sunshine Fire in the Boulder Daily Camera.

Credit: Adam Holloway