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
warren " Here's a good overview from EPA Region 1, New England: https://www3.epa.gov/region1/airquality/pm-aq-standards.html Although it's a bit jargony. " | Read more » about 5 years ago
liz "For future readers of this thread, @samr did repost here: https://publiclab.org/questions/samr/04-07-2019/how-to-interpret-pms5003-sensor-values " | Read more » about 5 years ago
liz " Thank you! " | Read more » about 5 years ago
liz "When i read the original poster's question, my takeaway is that this is a student working in a group that has already hooked up a plantower sensor ..." | Read more » about 5 years ago
liz " Thank you for writing in such an accessible manner @guolivar ! I really appreciate it " | Read more » about 5 years ago
sagarpreet " Hi @liz , The image source of the above formulae is : https://en.wikipedia.org/wiki/Air_quality_index The map made by purpleair community is he..." | Read more » about 5 years ago
jeffalk " Hi @samr. All the comments above are good and hopefully helpful and your questions are astute. I'm curious as to what led you to "air quality" a..." | Read more » about 5 years ago
guolivar " Quickly to your question of: For example, the first 6 are two sets of PM1, PM2.5, and PM10 concentrations. the first set are labeled "standard", w..." | Read more » about 5 years ago
liz " Hi @kkoerner, you wrote above that "Taking apart a PurpleAir and swapping out sensors is relatively easy, if there's a desire for a similar guide ..." | Read more » about 5 years ago
liz "Here's a link to a comprehensive thread from last year where @sagarpreet was exploring how to visualize a global layer of Purple Air readings. http..." | Read more » about 5 years ago
liz " hi @sagarpreet , could you provide a link to your source for the image of computing the AQI? thanks! " | Read more » about 5 years ago
liz "Hi @samr! So great to hear from you. Just to get everyone on the same starting point with this question, I looked up the datasheet for the pms5003..." | Read more » about 5 years ago
zengirl2 " I think @kkoerner may be able to answer this since he has done a lot of work with this sensor. " | Read more » about 5 years ago
warren " Hi @wu_ming2 - sorry we weren't able to connect you with some resources on this. This comment from @BrandonFeenstra may have some useful informati..." | Read more » about 5 years ago
warren " Hi @samr, would you be able to repost your last questions on https://publiclab.org/purpleair#Questions, and we can then try to get the word out a ..." | Read more » about 5 years ago
samr " hi. we are trying to use the pms5003 sensor for a school project to take air quality measurements. We don't have much experience with air qualit..." | Read more » about 5 years ago
SadiePrego "Definitely! " | Read more » about 5 years ago
warren "@wmacfarl also did you do your workshop with these yet? " | Read more » about 5 years ago
warren " Hi @sadieprego - would you like us to send you one of these? " | Read more » about 5 years ago
midol "some PMS5003 distributors specify that Mie scattering is used " | Read more » over 5 years ago
jeffalk " @warren, what is "helpful", as you know, depends on the intended use. Data from unknown and unsubstantiated sources can be unreliable depending ..." | Read more » over 5 years ago
kkoerner " NREL's SAM has access to NREL AWS Truepower files, you may be able to access and incorporate some of that data if you're looking to measure wind e..." | Read more » over 5 years ago
liz " https://www.windfinder.com/ " | Read more » over 5 years ago
joyofsoy " I'm going to share this on the Public Lab Twitter account to see if we can get some more input from others " | Read more » over 5 years ago