Air Quality Awareness Week Day 3: Citizen Science and Sensors

This blog is part of a series about air quality and your health. See Part 1 and Part 2

National Air Quality Awareness Week is May 3 - 7, and the Nevada Division of Environmental Protection (NDEP) is reminding Nevadans: "Healthy Air – Important for Everyone!” Throughout the week, we will be sharing helpful information and resources about Nevada’s air quality on this blog. Look for new air quality related themes each day!

Tracking Our Air Quality

Whether it’s natural causes (such as topography or the weather) or man-made causes (such as car exhaust or smoke stacks), many things can influence the quality of our air. Air quality fluctuates from place to place due to different environmental circumstances. In a word, air quality changes — and it changes all the time.

Most often, government agencies like NDEP use networks of large, advanced sensors to measure even the tiniest changes in pollution concentrations. These advanced sensors meet strict federal guidelines, and are considered “regulatory” sensors. Every time you go online to check the air quality in your community, you’re tapping into a statewide network of these regulatory sensors.

From Pahrump, to Elko, to Carson City, air quality monitors give us insight into the air outside, constantly documenting pollution concentrations throughout the day. NDEP places these specialized air quality monitors in communities with the highest populations and historically poor air quality. But we have some resources to support our more rural communities too.

Enter Portable Air Sensors

Portable air sensors are a low-cost alternative to more expensive regulatory sensors used by government agencies. Thanks to portable sensors, air quality around the world can be measured in real time by anybody with internet access. Portable air sensors are revolutionizing how we monitor the quality of our air.

Federal, state, and local air agencies have to follow strict rules about where to set up their regulatory monitors. While these monitors provide highly accurate scientific data, they’re too big and expensive to put everywhere. Portable sensors empower the public to monitor air quality in more places, compiling data much faster than the federal, state, and local agencies can on their own.

Here at NDEP, we embrace the revolution of portable air sensors too. We believe that directly engaging Nevadans through community science is key to monitoring and protecting our air.

But there’s a catch…

Though they are small and convenient, portable sensors simply aren’t as precise as NDEP’s large, regulatory sensors. Every regulatory sensor in Nevada is certified by the U.S. Environmental Protection Agency (EPA). As a result, we can be confident in the accuracy of the data they provide. Portable sensors, on the other hand, lack the same level of accuracy and precision, meaning that even though a sensor is reporting data, it may represent actual conditions. EPA scientists have found that sensors often overestimate or underestimate pollutant concentrations when compared to the regulatory-grade instruments that are operated in the same location.

A screenshot from PurpleAir showing pollution readings from portable sensors around the world.

Even with all the obstacles, portable air sensors still give us unique insight into air quality at the neighborhood level; this is useful, as the more advanced regaultory monitors are designed to provide information about air quality over a larger area – like a city or county.

To make data from smaller sensors more accurate, scientists with the EPA have developed a “correction factor” that’s applied to the data from PurpleAir sensors. This brings the data back in line with what a regulatory-grade monitor would read under the same circumstances. You can check out the corrected data on EPA’s Fire and Smoke Map.

How do I use a portable sensor?

Our team at NDEP, the EPA, and other public agencies are constantly working to better understand how to use portable sensors.

Based on what we’ve learned so far, here are a few suggestions and tips to keep in mind when using a portable air sensor:

  • Be mindful of the weather. Portable sensors are influenced by temperature and relative humidity. A large change in your air quality reading may have more to do with an incoming thunderstorm than actual pollution concentrations. Keep track of weather conditions and pollutant concentrations to account for biases or measurement errors.
  • Get a backup! If possible, always use two or more sensors in the same location. This may provide hints on their reliability.
  • Compare your monitor. Try to compare the hourly measurements of your sensor with a nearby state, federal or local regulatory air quality monitor. NDEP can help with this – send us your sensor, and we’ll pair it with one of ours for a week or two so you can see how the data compares. We’ll send it back, we promise!
  • Observe the area. Are there landscape features (walls, high buildings, or trees) that could block the free flow of air? This might make the air stagnate, inflate pollution concentrations, and block the sensor from measuring the pollutants. Is your sensor near a BBQ or fireplace? If possible, mount the sensor in a shady spot out of direct sunlight. Keep it away from vents or other local sources of pollution – even that delicious hickory smoke from your BBQ grill!
  • Watch for seasonal changes. Expose your sensor to air pollution during all seasons: to wildfires in the summer; to woodstoves in the fall and winter; to the relatively “clean” air in spring. When doing this, ask yourself if your sensor is responding as you would expect it to.
  • Join our community of clean air enthusiasts. Already own a personal air sensor? Join our Listserv for air sensor owners! Share your experiences with other users to compare readings and observations. Send us an email to join today!

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