Air Quality Monitors Compared: AirGradient vs Purple Air

Purple Air. The Pioneer in Low-Cost PM Monitors

Purple Air played a significant role in making low-cost air quality monitors accepted by the public and government institutions. There are now a significant number of studies available comparing the Purple Air monitors against reference instruments and proposing correction formulas to make them more accurate. It’s probably the most studied air quality monitor out there.

We at AirGradient are thankful for the impact of the Purple Airs and the way it paved the way for other low-cost manufacturers like us.

Purple Air Models

Purple Air has indoor and outdoor monitors. This comparison will only focus on the two most popular outdoor monitors, the Purple Air Classic and the Purple Air Flex. We’ll compare these to the AirGradient Open Air models O-1PPT and O-1PST.

Accuracy

The AirGradient Open Air uses the same Plantower PMS5003 module as the Purple Air Classic, so the monitor’s performance can be expected to be very similar.

This is confirmed by our global co-location project in which we test the accuracy of the AirGradient Open Air monitors worldwide.

Below is a chart comparing the raw data of Purple Air and AirGradient monitors in Anacortes, USA. The Purple Air monitor is in red, and the AirGradient is in blue. The two monitors are very well-agreed upon.

Dashboard & Map

The Purple Air monitors can be connected to the Purple Air dashboard and made public. Then, the monitor appears on the Purple Air Map. The purple air map is one of the most feature-rich air quality maps and has a lot of functionality. One of the key functionalities is the ability to apply different correction formulas, e.g. to make it more accurate for wildfire smoke.

The AirGradient Map currently has fewer features but is actively being developed, and we expect to add much more functionality over the next couple of months.

Purple Air recently stopped sharing data with openAQ, so historical data is no longer available on openAQ. Limited data can be downloaded through the Purple Air map.

Data Ownership

Purple Air places heavy restrictions on how you can use the data you collect with their monitor. The way the Terms are written makes it difficult to understand if your use case complies with them.

In contrast, the AirGradient Terms & Conditions do not limit your rights on data ownership or how you would like to use the AirGradient monitors.

Comparison Table by Model

The AirGradient Open Air, in its standard configuration, has one PMS5003 module and a CO2 module (model O-1PST). However, AirGradient also offers the O-1PPT model with two PM5003 modules if required.

Criteria Purple Air Classic Purple Air Flex AirGradient Open Air (O-1PPT) AirGradient Open Air (O-1PST)
PM 2x PMS5003 2x PMS6003 2x PMS5003T PMS5003T
CO2 None None None SenseAir S8
VOC Bosch BME688 Bosch BME688 Sensirion SGP41 Sensirion SGP41
NOx None None Sensirion SGP41 Sensirion SGP41
Temperature / Relative Humidity Bosch BME688 Bosch BME688 Built into PMS5003T Built into PMS5003T
Connectivity WiFi WiFi WiFi (Cellular Version available) WiFi (Cellular Version available)
RGB LED Light No Yes No No
SD Card Yes Yes No No
Data Ownership Restricted Restricted Unrestricted Unrestricted
openAQ Support No No Yes Yes
Open Source Hardware No No Yes Yes
Open Source Firmware No No Yes Yes
Price for Monitor USD 229 USD 289 USD 190 (as kit USD 125) USD 190 (as kit USD 125)
Price for API Pricing Pricing Free for now Free for now

Summary

The accuracy of the Purple Air and AirGradient monitors is similar, as they use the same Plantower PM modules. The advantages of the Purple Air are its better map application, SD card storage, and RGB LED (Flex model). The advantages of the AirGradient Open Air are its additional sensor modules, e.g., for CO2, open source and open data license, and a significantly lower price.

Contact us if you have any questions.

Disclaimer

Being a monitor manufacturer makes us obviously biased when comparing the AirGradient to other monitors. However, being an open-source hardware company we are by definition a lot more transparent than traditional companies and believe we can make a relatively fair and objective comparison.

by Achim Haug
May 14, 2024

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