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 "@guolivar @BrandonFeenstra @GreenFrogg @rockets @nanocastro do you have some information on this? Some folks are looking to build some sensor/datal..." | Read more » over 5 years ago
warren "@guolivar have you read over these reports and do they factor into your assessment of the Purple Air? Thank you both! " | Read more » over 5 years ago
warren "This is a GREAT post. Thank you so much!!! " | Read more » over 5 years ago
warren "Ah, yes, confirmed by @guolivar's post: https://publiclab.org/notes/guolivar/01-08-2018/thoughts-on-low-cost-air-quality-sensors " | Read more » over 5 years ago
warren "Quick update - the sensor in the Purple Air seems to be this one or one very similar, a laser based sensor with a fan -- the PMS5003 -- $30 shippe..." | Read more » over 5 years ago
stevie "Hi @BrandonFeenstra ! I had a group asking me about the Dylos this morning, so I went to the AQMD website and found the report for it like the one ..." | Read more » over 5 years ago
GreenFrogg "I don't have experience with the Purple Air. The page is an overview made by the Dutch institute of environmental health (RIVM). They coordinate. Y..." | Read more » over 5 years ago
stevie "@GreenFrogg I was checking out your list of sensors on this page and didn't see the Purple Air. Have you worked with it? what are your thoughts on..." | Read more » over 5 years ago
liz "This is a great thread! Excited to find this simple experiment. We might consider recommending this as an activity for people to try as they set up..." | Read more » over 5 years ago
warren "Hi, Jeff - if you can't get it to work, please feel free to email it to me at jeff@publiclab.org and I can try.  On Wed, Sep 5, 2018 at 1:34 PM \&..." | Read more » over 5 years ago
jeffalk "I'll try placing the graph again. I'm sometimes clutzy at this stuff! I'm trying to use jpg format. " | Read more » over 5 years ago
guolivar "I'll try to unpack a couple of things here. The use of zero filters is standard practice as a quick check of particle instruments. It is used to t..." | Read more » over 5 years ago
zengirl2 "@jeffalk does it work if you convert image to jpg format? " | Read more » over 5 years ago
jeffalk "I tried to drag an image, tried copying and pasting, tried putting the image into a WORD document and dragging or pasting, you see the results above. " | Read more » over 5 years ago
Ag8n "I agree that the original data should be used. But, if the sanity check is not zero, that result should also be recorded, or at least noted. " | Read more » over 5 years ago
warren "you should be able to just drag in an image to the text area! On Tue, Sep 4, 2018 at 6:05 PM \<notifications@publiclab.org> wrote: Hi! Ther..." | Read more » over 5 years ago
jeffalk "Nice "sanity check" for pm "real time" monitors. I'd suggest it is always good practice when testing to make use of original data, in the case of..." | Read more » over 5 years ago
zengirl2 "@warren Cool experiment. So your dip in the top graph--do you think that is expressing less traffic due to start of holiday or is it raining there? " | Read more » over 5 years ago
jiteovien "@bigmit37 I can't answer that for sure but I would recommend getting the one designed for outdoor use. I'm not sure if there are any differences in..." | Read more » over 5 years ago
warren "OK, I'm removing the cover now, wow that seems to have worked! " | Read more » over 5 years ago
warren " OK, it's every 10 minutes, and I just covered it: " | Read more » over 5 years ago
warren "I can try this right now, at the Providence Purple Air sensor: https://www.purpleair.com/map?#12/41.8091/-71.4266 " | Read more » over 5 years ago
bigmit37 "@jiteovien It seems there are three versions, two for outdoors and one for indoors? Does the indoor one also require Wifi?It seems the outdoos on..." | Read more » over 5 years ago
jiteovien "@bigmit37 PurpleAir is a popular one. Read about it here " | Read more » over 5 years ago