Amber Vigh had taken the usual precautions when bringing her nine-year-old son, Carter, to summer camp in July 2023. There were no fires near their home in British Columbia, Canada. Her air quality app showed low levels of pollution. She could not smell any smoke.

Carter, a music-loving Lego enthusiast who had asthma, brought along his smiling shark tooth-patterned emergency kit that held an inhaler, allergy pill and EpiPen. When smoke did roll in from the north, Vigh took him indoors.

But at home that evening, Carter began to cough uncontrollably. Vigh and her husband, James, followed the doctors’ checklist – emergency inhaler, drink of water, steroid inhaler – and gave him a bath to cool down. Then, “all of a sudden, he started coughing again like crazy”, said Vigh.