PurpleAir
purpleair

The [PurpleAir](https://www.purpleair.com/) is one of many low cost devices that use laser optical particle counters to estimate particulate matter mass concentrations in air for PM2.5 and PM10. Other similar devices include the [Dustduino](https://publiclab.org/wiki/dustduino), [Speck](https://publiclab.org/notes/chrisbartley/04-15-2014/speck-particle-monitor), [Dylos](http://www.dylosproducts.com/?gclid=Cj0KCQjw5NnbBRDaARIsAJP-YR_IQiQC0876PaQmo6lWAuRPJ5FG3oh65dc7rsf95xSqDd0Wdqrs6OYaAsxtEALw_wcB) and more. The PurpleAir costs around $200 and provides real time air quality data that can be used to understand indoor or outdoor environments and conduct environmental investigations on air quality. **The intention of this page is to create a central location to discuss successful (and unsuccessful) use cases of the PurpleAir and problem solve together. Please contribute any experiences you've had with the PurpleAir. Perhaps consider visiting https://publiclab.org/simple-air-sensor to see the start of a barebones kit that is kicking off the development of a well-supported, open source air sensor similar to the PurpleAir.** ## Why use one? Every state in the US is mandated by the Environmental Protection Agency to create air quality sensor networks to monitor the six pollutants that the EPA defines as hazardous - Ground-level ozone, Carbon monoxide, Sulfur oxides, Nitrogen oxides, Lead and Particulate Matter. Read more about [particulate matter](https://publiclab.org/wiki/pm#Background+Information) here. However, due to the huge cost upwards of $25,000 associated with Federal Reference Method (FRM) and Federal equivalent method (FEM) sensors, most cities only have a handful of sensors, sometimes just one, measuring each category of pollutant. In addition, FRM sensors often have a lag of several months for quality control before the data is publicly accessible. Optical sensors provide a way to get near real-time data on the particulate matter in your home or community and to have autonomy over the locations being monitored. ##How it Works [This page](https://publiclab.org/wiki/optical-pm) does a great job of explaining how laser optical particle counters work in detail. But, the most important things to know when deciding to use an optical particle counter like the PurpleAir is that: 1. The data the PurpleAir (and other optical counters) produce is an _estimation_ of particulate mass concentration that relies on several assumptions for shape, diameter and density. The quality of your data will depend on those assumptions as well as environmental considerations such as humidity, light and temperature. 2. Because of the fact that optical counters rely on these assumptions, the data produced by them are _not_ FRM or FEM certified. That being said, there have been a number of academic studies that have quantified the performance and limitations of some of these optical sensors to help you choose which one to use depending on what you are trying to sense and what level of performance you are looking for. The EPA has an excellent summary of these studies in this table [here](https://www.epa.gov/air-sensor-toolbox/evaluation-emerging-air-pollution-sensor-performance). A higher R^2 value means better performance. [This page](https://publiclab.org/wiki/optical-pm) has some more links of studies to check out if you scroll a bit. [Here](http://www.aqmd.gov/docs/default-source/aq-spec/field-evaluations/purpleair---field-evaluation.pdf) is a study specific to PurpleAir. ## Use Cases - PurpleAir maintains a [map](https://www.purpleair.com/map?#0.27/0/-30) of every user's data from around the world. Check it out. - A use case in [Utah](https://www.good4utah.com/news/local-news/dirty-air-monitors-are-they-telling-us-the-whole-truth/382744964) - A use case in [California](https://cleantechnica.com/2018/07/09/my-new-favorite-gadget-a-purple-air-air-quality-monitor/) - [This facebook group](https://www.facebook.com/groups/purpleair/) includes people who own a PurpleAir and discuss their experiences - [This blog](https://www.wxforum.net/index.php?topic=33031.0) has some dialogue about various use issues Please add your experiences with PurpleAir too! ## Suggestions for conducting particulate matter investigations [This page](https://publiclab.org/wiki/general-environmental-monitoring-study-strategies) summarizes important considerations before starting an investigation. To add onto those, specifically in regards to air quality, here are some suggestions. Before ordering a sensor, check out the data that is freely available to you online. [Visit your state's department of environmental management website](https://www.epa.gov/home/health-and-environmental-agencies-us-states-and-territories) and their air quality section. With some poking around, you can find their ‘Air monitoring network plan’ which will show you the _exact locations_ of all of their different FEM/FRM sensors and what pollutant they are measuring. This can help to identify gaps in their monitoring network that you may be interested in. [AirNow](https://www.airnow.gov/index.cfm?action=airnow.main) has national daily data from FEM monitors. You can search for your zip code and see the live air quality forecast. This can be used to help inform your day to day movements especially if you are an asthmatic. You can also download data* from FRM monitors [here](https://www.epa.gov/outdoor-air-quality-data/download-daily-data). This is really cool because you can specify what data you want and it will generate an Excel file for you. You can then start making plots and figures to compare different time periods and locations. [Check out this post](https://publiclab.org/notes/jiteovien/08-01-2018/air-quality-data-visualization-no-coding-necessary) which used this online EPA data to create some visualization of the monitoring in Rhode Island. *NOTE: As mentioned earlier, the FRM data has a lag for quality assurance reasons. For example, the most current Rhode Island data is for May 2018. (It is August at the moment this is being written). Everyone, whether or not you own a Purple Air has free access to the Purple Air's database of global sensors. Read more about this in the activity [Download & Analyze your Purple Air data](https://publiclab.org/notes/jiteovien/08-28-2018/download-analyze-your-purple-air-data?_=1535473842). ## Questions Questions can be either frequently asked questions, or "next step" challenges we're looking to solve. [questions:purpleair] ## Activities Activities show how to use this project, step by step. [activities:purpleair] ## Other things to know about using your Purple Air The PurpleAir sensor has two 'channels' that measure data. Channel A and Channel B. Each channel has a 'primary' and 'secondary' data set. The data that Channel A measures is described below: PrimaryData - field1: PM1.0 (CF=ATM) ug/m3 - field2: PM2.5 (CF=ATM) ug/m3 - field3: PM10.0 (CF=ATM) ug/m3 - field4: Uptime (Minutes) - field5: RSSI (WiFi Signal Strength) - field6: Temperature (F) - field7: Humidity (%) - field8: PM2.5 (CF=1) ug/m3 This is the field to use for PM2.5 SecondaryData - field1: 0.3um particles/deciliter - field2: 0.5um particles/deciliter - field3: 1.0um particles/deciliter - field4: 2.5um particles/deciliter - field5: 5.0um particles/deciliter - field6: 10.0um particles/deciliter - field7: PM1.0 (CF=1) ug/m3 This is the field to use for PM1.0 - field8: PM10 (CF=1) ug/m3 This is the field to use for PM10 particles/deciliter is a particle count per volume measurement. ug/m3 is the particle mass concentration - the popular method of measuring particulate matter. Channel B measures the exact same primary and secondary data. This is likely just done for robustness just in case one of the channel fails or has an error. These setup instructions are included with the Simple Air sensors and can be reprinted Purple_Air_Instructions.pdf ...


Author Comment Last activity Moderation
patcoyle "Another approach is to look at the elevation shown for the cursor location in Google Earth Pro, as in this example (it is small, hard to see in the..." | Read more » about 2 years ago
liz "cool! thank you " | Read more » about 2 years ago
rebeccaMw "I found a free app for Apple devices that uses the GPS in your phone to determine the altitude of the specific area. It's called "My Altitude." It ..." | Read more » about 2 years ago
bhamster "Thanks so much for the update @wu_ming2, glad to hear the push notifications are still working well for you! " | Read more » about 2 years ago
wu_ming2 "@bhamster I just became aware of this thread. My profile has notifications settings on but received none. Who knows why. For the record my soluti..." | Read more » about 2 years ago
wu_ming2 "Thanks @bhamster for the mention. After two years push notifications still work for me. Received more than 8k of them saving countless time by non..." | Read more » about 2 years ago
bhamster "Glad you found these helpful, @purpleairfan! Were you able to try anything out or find a solution? " | Read more » over 2 years ago
stevie " @stevie has marked @travislondon as a co-author. " | Read more » over 2 years ago
purpleairfan "these are very helpful, thanks so much!! " | Read more » over 2 years ago
bhamster "Hi @purpleairfan! You might find some ideas in this related question and its comment section: https://publiclab.org/questions/eustatic/01-20-2021/h..." | Read more » over 2 years ago
liz "@liz awards a barnstar to ottinger for their awesome contribution! " | Read more » over 2 years ago
AnemometricalTwoStep "+1 One of the channels in my PurpleAir started reporting a value of 0 constantly. I suspect I’m going to have to take it apart and replace or clea..." | Read more » over 2 years ago
warren "Just noting also a big round up of notes on humidity and fog with optical sensors here: https://publiclab.org/questions/sarasage/08-10-2021/is-the..." | Read more » over 2 years ago
Onlinemagazine "Excellent post, thank you for share this amazing information. " | Read more » over 2 years ago
Ag8n "For the most part, my experience was on the manufacturing end. And the answer would be very similar, but stated quite differently " the cost bene..." | Read more » over 2 years ago
denissebn_06 "This might be some useful information for you @sarage Check out the report linked " Making most of monitoring". " | Read more » over 2 years ago
bhamster "@LESBreathe, this post and the report linked in it might be helpful to check out " | Read more » over 2 years ago
badoopremiumapk "PurpleAir is a community air monitoring system of PM (10, 2.5, 1.0) air pollution sensors. The PurpleAir system is composed of many sensors that ar..." | Read more » over 2 years ago
seankmcginnis "@denissebn_06 - Kriging is a type of spatial interpolation that can estimate values for unknown locations based on known values/locations. This is..." | Read more » over 2 years ago
amocorro "Here's some introductory information that might be helpful: https://desktop.arcgis.com/en/arcmap/10.3/tools/3d-analyst-toolbox/how-kriging-works.ht..." | Read more » over 2 years ago
sarasage "This is really, really cool @seankmcginnis " | Read more » over 2 years ago
seankmcginnis "My first barnstar!!!!!!!!! Thanks @liz " | Read more » over 2 years ago
liz "@liz awards a barnstar to seankmcginnis for their awesome contribution! " | Read more » over 2 years ago
bhamster "This is absolutely wonderful, @seankmcginnis! Thanks for responding to needs brought up on the Open Calls by creating this custom code and sharing ..." | Read more » over 2 years ago