I wrote this which calculates AQHI-Plus (and other indices) from the raw data from Squamish Elementary: chiefcam.com/tools/air-qu...

This sometimes reads even lower than the EnvCanada value, so I do wonder if they're also doing weighted averaging if neighbouring sensor sites have higher readings.

Squamish's sensor site is outside Squamish Elementary on Buckley Ave downtown, which is both very low elevation and quite close to the water.

This probably means sees less wildfire smoke pollution, and reports a lower reading, than most Squamish residents experience.

I think Environment Canada is probably limited to only using their own sensors, which are a bit few and far between, map here: www.env.gov.bc.ca/epd/bcairqua...

Simplistically, AQHI-Plus is calculated by taking the PM2.5 reading in µg/m3, dividing it by 10, and then rounding it up. So a PM2.5 reading of 95µg/m3 would result in an AQHI-Plus index of 10. (Simplistically because this is only how it works when PM2.5 is much higher other pollutants, like now)

AQHI-Plus indicates a higher (worse) value when only PM2.5 levels are high, as opposed to AQHI which will show limited increases when only one type of pollutant is high.

AQI is a US measurement, I'm guessing you mean AQHI-Plus, which is the standard for measuring air quality in BC?

AQHI-Plus is a modification of AQHI that BC introduced in 2021 to be more responsive to wildfire smoke.