Purple Air Monitoring Project


On March 16, 2018, Citizens for Clean Air launched the Purple Air Monitoring Project.

Within the Grand Junction airshed, there is only one EPA approved  particulates monitor. It is located at the top of the Powell Building in downtown Grand Junction.

EPA particulates monitors are expensive; up to tens of thousands of dollars. Yet particulate concentrations are likely to vary dramatically across the valley because of the extremely varied terrain. One monitor provides limited coverage and hinders our understanding of what may be taking place. In turn, this limits our ability to provide good data, necessary to address community concerns about health effects. Even short term exposure to high levels of particulates can cause problems, especially for children, the elderly, and those who already suffer from respiratory and other ailments.

Purple AirA Solution

To address the shortage, CCA member Gerald C. Nelson, PhD researched low-cost air quality monitors, worked with manufacturers to test their products, and ultimately recommended the purchase of monitors from a company called Purple Air LLC.

As of July, 2018, there are over 30 Purple Air monitors in place from Mack to Palisade and from northern Grand Junction to Whitewater!

What is Tracked?

Particulates of varying sizes, ranging from 0.1 to 10 microns, are tracked by the monitors. This date is then converted  to an EPA-style Air Quality Index (AQI), based on the mass of particles of 2.5 microns or less per cubic meter of air (the PM 2.5 measure). All these data are displayed at the Purple Air website map for viewing the information. If you click on any one of the circles/ovals on the map with numbers in them, a new window opens up with options to explore the data.

How to use this information

If you suffer from asthma and have plans to run errands in a different part of town, you might want to check the air quality there. Or you could monitor the changes in particulates near your home and see if you notice any correlation between asthma attacks and changes in particulate pollution.

If you see an unusual spike in particulates at a location near you, consider taking a quick look in that direction to see whether there are any problems.  If you are a biker/runner, take a look at the map and consider scheduling your activities at a time and place with less pollution.

Thank you to Grand Valley residents who have either agreed to host monitors at your homes and/or donated to help fund the study. We are also thankful to Alpine Bank for placing monitors at each of their five Mesa County locations, to Conservation Colorado and donors of the Western Colorado Community Foundation for helping to fund the project, and to Desert Ecosystems and Restoration for their original funding to explore prototypes.

Order a Purple Air Monitor: Go to www.purpleair.com

How to Install and Care for Your Purple Air Monitor

For the most part, PA monitor installation is straightforward. Go to the Purple Air website (www.purpleair.com), click the Install link near the top middle of the page and follow the directions.

Here’s the basic process

  1. Plug in the monitor somewhere relatively near your wifi router.
  2. It starts sending a wifi signal, which you need to switch your device to (laptop, tablet, smartphone, etc). Start at the install page, then click to the next page where it will tell you to go to your device’s wifi setup section and look for a wifi signal that starts with something like PAmonitor xxx.
  3. Once you choose it and your device is connected to the PA monitor wifi signal, return to the web page. This process can take a while. You’ll know if it was successful if the next page shows you a list of potential wifi signals it detects (might get the neighbors, etc). Choose the one for the location where you are installing. Next it will ask for a password. If you enter it and everything goes fine, you’ll get a new set of information at the top of the page, including “Success” with the MAC id and other information.
  4. The next step is to register the device. Theoretically your device should have been switched back to a ‘real’ wifi address (Normally your wifi address). Check if you have been. And if not, do so now.
  5. Click the Next link and you should be taken to a table where some of the information is filled out (from the previous step) and you’ll need to fill in more. Some key points:
    1. The first email address to enter must be the one used in the purchase process for the monitor. This email address is connected at the Purple Air database to all the monitors CCA has purchased. If you are installing someone else’s monitor, you’ll need to use the email address they used when the monitor was purchased.
    2. Give the monitor a name. We like to use “CCA xxx” where xxx is some text that indicates where the monitor is located, such as “CCA Quail Run” or CCA Redlands”.
    3. The setup process is remarkably good at putting a pin on a map, but if it’s off, you can drag the pin to the location where the monitor will be installed. This then fills in the latitude and longitude boxes for the location.
    4. The owner name and email address can be whatever you like. It can also be changed at a later date.
    5. Finally, click Register. If all goes well, you’ll be able to see the monitor on the Purple Air map in a minute or so.

Now unplug the monitor, take it to its final location, plug it into the power outlet and proceed to install the monitor. Ideally this will be somewhat sheltered from the elements, and direct sunlight.

Potential installation problems

Most issues have arisen at step 3. Sometimes you have to repeat it several times or the success message is not obvious. If you think you have chosen the correct SSI and entered the correct password, go to the Registration page and fill out the information. If you have been successful in making the wifi connection, the Purple Air page will show up with a colored circle or oval with the local particulate API displayed. If the wifi connection wasn’t made, you’ll need to start the install process over. In that case, you don’t need to fill out the registration information again. It’s already in the Purple Air data base.

Check to see that the outdoor electrical outlet you are using has power, and is not connected to switch that could turn it off inadvertently. The outlet needs to have continuous power.

Cleaning a monitor

Occasionally the PurpleAir monitors may need to be cleaned.  This need is evidenced by large discrepancies in the readings between sensor A and sensor B.  These differences between sensors can be quite large, with one sensor reading 400+ while the other reads 5 or less. First look into the bottom of the PurpleAir monitor with a good flashlight. Remove any insect cocoons. A small needle nose pliers works best. Next use a gentle supply of compressed air to blow out both sensor modules.  A variable speed, battery operated leaf blower set to its lowest speed and held 2-3 feet away from the monitor works well. A gentle stream of air from an air compressor or a can of compressed air for computer cleaning should also work.  

After a successful cleaning the sensors should slowly return to reading the same.  This could take a couple of hours.

Once a sensor goes rogue, it could take 3 days or more for the R2 calculation to return to normal (something close to 1).

In areas with many Cottonwood trees, this sensor fouling problem could occur more often.