How air quality is measured when wildfire smoke rolls in

Wildfire smoke hangs over the Albert Street bridge in Regina on May 30, 2025. (CTV News Regina Skycam)

With smoke from wildfires spreading throughout Saskatchewan, air quality statements and warnings have been and continue to be in effect for many parts of the province.

Environment and Climate Change Canada (ECCC) measures air quality in several ways when determining if health risks are elevated prompting advisories to be put in effect. That includes when smoke from wildfires moves in.

Meteorologist Danielle Desjardins says to simplify the process for the public, the weather office uses a scale called the air quality health index (AQHI) with a one to 10 scale. Anything from a one to a three on the scale means minimal health risks, four through six means moderate, and seven through 10 means high. Anything above 10 is rated as extreme.

Desjardins said 10-plus readings have been and are expected to continue throughout the province.

Fine particles represent the main health risk with wildfire smoke, ECCC says.

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Smoke from wildfires is a mix of gases, particles and water vapour that contain ozone, methane, sulfur and nitrogen dioxides, carbon monoxide, volatile organic compounds, fine particle matter (PM 2.5) and polycyclic aromatic hydrocarbons (PAHs), according to ECCC.

“When air quality gets poor, it’s mainly due to something we call PM 2.5, particulate matter 2.5,” Desjardins said.

The level of smoke or pollution in the air is then determined by a parts per million measurement.

“So, let’s say that the PM 2.5 is 60. That means that out of a million molecules of dry air, 60 of those will be particulate matter 2.5,” Desjardins said.

ECCC will issue air quality statements when the AQHI reaches moderate and high levels and warnings when it reaches extreme levels.

As of Friday, the province said 16 wildfires are burning around Saskatchewan, seven of those are considered not contained. However, wildfire smoke can travel thousands of kilometres and fires from other provinces and the U.S. regularly bring smoky conditions to Saskatchewan.

On Thursday, Premier Scott Moe declared a provincial wildfire state of emergency.

A smoke forecast map can be seen here.