High pollution levels have triggered an air quality advisory for Vanderhoof.
The Environment Ministry says there are high concentrations of fine particulate matter in the community.
Officials advise residents with chronic underlying medical conditions to postpone any strenuous exercise until the advisory is lifted.
Exposure is a particular concern for infants, the elderly, and those with diabetes, lung, or heart disease.
An air quality advisory is also in effect for Prince George.
Real-time air quality measurements and information about the health effects of air pollution can be found at the BC Air Quality website.