Comparing PurpleAir Sensors With Expensive Government Monitors

During the Summer of 2017 the interior of British Columbia experienced an unprecedented forest fire season with wood smoke bathing much of the province in particulate pollution.

In Kamloops and elsewhere, community groups and individuals have been setting up low-cost air quality sensors made by companies like PurpleAir and more recently SensorUp.

How do these sensors compare to government air quality monitors which often cost hundreds of times more?

Below is an overview comparing three of several PurpleAir sensors in Kamloops to the government monitor located on the Kamloops Federal Building with respect to PM2.5 levels during the months of July and August 2017.

For comparison purposes, two PurpleAir sensors are within 1km of the Kamloops Federal Building.

Here's what the government monitor yielded during this timeframe based on a one hour averaging period.

Below is the same averaging period for the PurpleAir sensors located on Lorne Street and Strathcona Terrace.

Although some of the readings are both lower and higher for the PurpleAir sensors when compared to the government monitor once levels exceed 200 micrograms/m3, the overall patterns map extremely closely. This suggests that PurpleAir and other low-cost sensor technology can and should play a role in providing government and others with quick, accessible, realtime readings that have a high degree of confidence. This is especially the case in regions with variable topography, distributed point source pollution generators, and other local climatic effects.

Low-cost sensors typically measure only particulate matter, and are therefore not a replacement but an adjunct to more expensive monitoring stations that also collect data on ozone, NO, NO2, NOX etc.

Here's another example from Upper Sahali from a PurpleAir sensor on Monmouth Drive. Note the exact same pattern. This sensor is at an elevation of 600m versus the 350m elevation for the government monitor.

More analysis is to come, and our team member Dr. Michael Mehta is comparing 10 PurpleAir sensors to the Kamloops Federal Building for a peer reviewed scientific article.


  1. Grass roots science as it should be done... congratulations, Dr Mehta.


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