Citizen Science

Putting Hazelton’s air pollution on the map

Dave Stevens

Photo: adrimcm via Flickr

Technological change is enabling citizens to monitor air pollution. Using a new generation of laser particle counters to provide real-time measurement of concentrations of various-sized particulate matter (PM), PurpleAir sensors are easy to install, requiring only a power outlet and WiFi. They use WiFi to report in real time to the PurpleAir online map, which provides both measurements and an Air Quality Index (AQI) reading.

The Village of Hazelton is a postcard-pretty old-west-style settlement on the banks of the Skeena river near the confluence of the Bulkley in northwest BC. That’s in the spring and summer. But in the fall and winter the picture isn’t as pretty, with wildfire smoke and dirty chimneys adding their distinctive pall to the view. Spring grass burning doesn’t help either.

The people who live here know the problem but don’t get much satisfaction. So the Bulkley Valley and Lakes District Airshed Management Society (AMS) partnered with the Village to start creating a written record of the concentration of particles in the air. The money needed – $400 total – was split down the middle and the AMS bought, tested, and deployed the PurpleAir monitor. By fall, the AMS will place three more sensors at Gitanyow, Moricetown and Telkwa.

The PurpleAir initiative started with technological change and some upset people in Utah. They worked with the college of engineering at the University of Utah to design, build, and sell the sensors to encourage concerned citizens to measure air pollution levels.

The people who live here know the problem but don’t get much satisfaction.

The new enabling technologies are the internet and low-cost laser particle counters. The sensor unit is about the size of a softball and includes wifi, particle counters and temperature and humidity sensors. Screw the unit to a wall, plug in the 110V and connect to the mothership map. The map shows the sensor locations; panning, zooming, and clicking takes you to current readings at any online connection.

The pollution data gathered is about different sizes of particles, from PM0.3 (ultrafine) to PM10 (coarse fraction). The air quality index (AQI) popup box on the online map is well designed and deceptively simple – there’s a lot there. Of greatest health interest is PM2.5, the fine fraction. There are current conditions – updated every ten seconds – but there are also one-hour, 24-hour and one-week averages.

All the data reported to the map site is archived. This public record of conditions is what we hope will be effective in drawing attention to the issues.

The BC government particulate monitors are about $28,000 a pop and are based on a more precise technology called beta attenuation, with the acronym BAM. Well, the thing about the BAMs is the $28,000 part. That’s why I haven’t got one. But the purple air monitor is 99% of the BAM at about 1% of the cost. Good enough for me. The Southern California Air Quality Management District did a co-located test with PurpleAir sensors beside BAMs and found very good correlation. Mostly the readings are accurate and we aren’t doing a doctoral thesis, just clarifying where the problems are in an impartial way, to support a healthy intervention.


Dave Stevens is the president of CHOKED, a small very non-profit environmental group in Smithers, BC.

About the AQI: Different countries have different air quality indexes; the numbers shown on the map are from the US and are different from Canadian usage. Please take note when examining readings on the PurpleAir site (US AQI) versus BC Environment’s readings, which use the Canadian standard.

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