Which Sensor to Choose

[PurpleAir]

PurpleAir offers different sensors that all uniquely suit different needs. Once connected to WiFi, all of these sensors appear on the PurpleAir map, where data can be viewed and shared. With proper installation, PurpleAir sensors are weather resistant. Additionally, any sensor with two laser counters calculates a confidence score on the map.

You can view details about each sensor model below and purchase your own sensors at Products – PurpleAir, Inc..

You can learn more about what PurpleAir sensors measure and how they work here.

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PurpleAir Touch

The PurpleAir Touch contains a single laser counter for particulate matter data collection, as well as a BME688 from Bosch, which is the component responsible for measuring temperature, humidity, pressure, and total volatile organic compounds (TVOCs). The VOC readings are currently experimental and we are unsure what they indicate.

The Touch contains a full-color LED that glows according to the US EPA PM2.5 air quality index. Double-tapping the sensor cycles through several brightness levels including off. Designed for indoor use, the Touch sits comfortably on a counter or tabletop.

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PurpleAir Zen

The PurpleAir Zen contains two laser counters for particulate matter data collection, as well as a BME688 from Bosch, which is the component responsible for measuring temperature, humidity, pressure, and total volatile organic compounds (TVOCs). The VOC readings are currently experimental and we are unsure what they indicate. The laser counters are built into a quick-release system, so they are easy to access and replace.

The Zen has an SD logger for offline data collection but does not come with a micro SD card. The Zen includes a full-color LED ring that glows according to the US EPA PM2.5 air quality index. Double-tapping the sensor cycles through several brightness levels including off. Designed for indoor or outdoor use, the Zen has a couple of swappable base mounts. The indoor base is designed to sit comfortably on a counter or tabletop. The outdoor base is designed to be mounted onto a wall or post.

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PurpleAir Flex

The PurpleAir Flex has two laser counters for particulate matter data collection, as well as a BME688 from Bosch, which is the component responsible for measuring temperature, humidity, pressure, and total volatile organic compounds (TVOCs). The VOC readings are currently experimental and we are unsure what they indicate. The laser counters are built into a quick-release system, so they are easy to access and replace.

The PurpleAir Flex contains a microSD card logger for offline data collection but does not come with an SD card included. The Flex includes a full-color LED viewable inside of the device housing that glows according to the US EPA PM2.5 air quality index. Designed for outdoor use, the Flex is meant to be mounted onto a wall or post.

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PurpleAir Classic and Classic SD

The PurpleAir Classic contains two laser counters for particulate matter data collection, as well as a BME280 from Bosch, which is the component responsible for measuring temperature, humidity, and pressure. The Classic is not capable of measuring VOCs. Designed for outdoor use, the Classic is meant to be mounted on a wall or post.

The PurpleAir Classic SD contains all of the features of the Classic, as well as an added SD logger for offline data collection. The Classic SD does come with a micro SD card.

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Learn More

• Sensor Owner’s Guide
• Sensor Coverage Area
• What Do PurpleAir Sensors Measure and How Do They Work?

[Mark_from_Pittsburgh (Mark Dixon)]

It looks like the Flex contains PMS-6003 laser counters while the old PA-II devices use the PMS-5003 laser counters. Can anybody confirm that form me and also potentially dive into the nuanced differences between those two types of laser counters? If I have a bunch of both types deployed in the field, will I be able to notice a difference in readings? Will they be reasonably comparable or more like apples to oranges?

Thanks!

Always monitoring,
Mark

[Mark_from_Pittsburgh (Mark Dixon)]

Here is a link I found that describes the difference. Curious to know if this holds up to scrutiny from others on this forum: Review: Node-S by Clarity – See The Air.

Quoting from the page: “The PMS6003 is a dual laser version of the PMS5003, for longer lifetime and has been proved to be very accurate and a better fit for particles with an aerodynamic diameter smaller than 2.5 microns (PM2.5) which makes it a perfect candidate for urban environments and vehicle emissions. Of course, it can also measure PM10 and PM1.0.”

[Robert]

I would like to get the Flex as well, for reasons you’ve highlighted, plus the VOC measurement. But as understood, determination of actual accuracy numbers is pending some testing Purple Air is either doing, or waiting on a 3rd part to do.

Regards,
Robert

[Ethan]

We are told that the accuracy of the PMS6003 laser counters should be improved, especially with PM10 measurements. However, @Robert is correct that they are being evaluated, and we are waiting to hear results back.

[Robert]

Hi Ethan,

Did you have an ETA on those results?

Thanks,
Robert

[tc10 (Bruce)]

Will the improvement be a firmware update or …? any updates on this?

[Mark_from_Pittsburgh (Mark Dixon)]

Do you have those results in yet? Is the PMS6003 accuracy updated to better match the original PA-II readings with PMS5003 units?

[Ethan]

Our apologies for the delay. AQ-SPEC has released an evaluation on the PurpleAir Flex sensor here: PurpleAir PA-II-FLEX.

[Mark_from_Pittsburgh (Mark Dixon)]

Thanks! I reviewed the PA-II classic and FLEX models on that AQ-SPEC website and found that the PA-II-FLEX seems to have worse performance than the PA-II classic, at least as indicated in the language in the “Discussion” for each monitor for PM1.0, PM2.5, and PM10. I made a chart to highlight the differences:

(EDITED ORIGINAL POST TO SWAP IN GRAPHICAL VERSION OF TABLE BELOW)

Do you have any comments on these differences? I would prefer to go with the PA-II FLEX for future purchases, but this information gives me pause. How will they compare to the PA-II classic models? Do you plan any updates to the FLEX that could potentially remedy this difference?

Here are the exact documents that I’m using to assemble this information:

http://www.aqmd.gov/docs/default-source/aq-spec/field-evaluations/purple-air-pa-ii—field-evaluation.pdf?sfvrsn=11

http://www.aqmd.gov/docs/default-source/aq-spec/field-evaluations/purpleair-pa-ii-flex—field-evaluation.pdf?sfvrsn=8

Thanks for your input!

Best,
Mark

[Mark_from_Pittsburgh (Mark Dixon)]

One addition - it also seems to me that the FLEX I have at my home tends to show higher EPA PM2.5 AQI scores than the PA-II Classic (also at my home) when the levels are in the high yellow or orange. The levels correspond well in the green zone. Has anybody else noticed a similar kind of issue?

[Mark_from_Pittsburgh (Mark Dixon)]

Here’s another visual examples of the difference between the Classic and Flex. Note how the divergence gets bigger at higher pollution levels…

[Kurvenal]

Thanks for the helpful comparison.

I have to replace the laser counters in my Classic, and was wondering whether it was worth upgrading to the Flex instead, but based on your postings it sounds like it is worth hanging on to my Classic and getting new PMS5003 sensors.

I am interested in any updates on comparing the different monitors if anyone has any.

[tc10 (Bruce)]

so if buying today, which should Ibuy?

[Kyle_D]

Resurrecting a post that has been quiet, but rather important (in my mind) since I am looking to add another sensor now has this been addressed in the Flex / Zen? I would very much like to get the Zen, but the classic is clearly the better performing model unless something has changed when I review the reports.

[tc10 (Bruce)]

any updates on stats or firmware fixes for this?

[h_g]

wondering the same. looking to purchase soon and interested in the flex - but given wildfire possibilities in my area, most concerned with accuracy.