An air quality advisory has been issued for the Comox Valley.
Meteorologist Earle Plain says the calm weather is trapping fine particulates near the surface.
He says air conditions will improve during the day as the air warms up, but the particles will build again overnight.
Those with chronic medical conditions, especially conditions like asthma and heart disease are advised to avoid strenuous activity until the weather changes.
Plain says he expects the advisory to stay in place for a few days.