34 homes have been evacuated as the massive moorland fire near Stalybridge reaches its third day.
People are being told to keep doors and windows closed, not to drive with the car's vents open, and to carry any medication for breathing conditions.
Union says the growing risk represents "another strain on dwindling resources."
The massive moorland fire in Saddleworth is now being investigated as arson.
More than 100 firefighters from Greater Manchester Fire and Rescue Service are continuing to battle against 'unprecedented' moorland fires.