Satellite measurements show many forest fires surrounding Kamloops and Kelowna during sampling (Figure ). Fire locations were gathered from the Fire Information for Resource Management System (FIRMS) U.S./Canada, using data from VIIRS NOAA-20, VIIRS S-NPP, MODIS Aqua and MODIS Terra. Forests in the burnt regions primarily consist of trees in the Pinaceae family, such as Douglas-fir and lodgepole pine. Back trajectories suggest that the field samples contained smoke from fires of varying distance from the collection sites and had an atmospheric age of approximately 12 hours or less (Figure ). The back trajectories were run with the HYSPLIT transport and dispersion model on the READY website from NOAA Air Resources Laboratory (ARL). Back trajectories were run once every 12 hours during the sampling period with a starting height of 0 m and using GFS meteorology (0.25 degrees, global).