Air quality in Billings started at unhealthy levels early in the morning, but for most of Wednesday, it has been registering at moderate, which may be a concern for sensitive people.
The Montana Department of Environmental Quality's "Today's Air" website states the moderate air quality can be a problem for those with respiratory symptoms for older adults with cardio-pulmonary disease.
Some in the medical field suggest avoiding even the mildest outdoor activities while others advise limiting time outside.
It's especially important for sensitive people to be careful if the quality moves in the unhealthy to hazardous levels.
Those in the medical field say the concern is breathing in particulate matter.
"It's still just best to stay inside when the smoke's in the air because even if you're doing some physical activity, you're very healthy, that smoke can still irritate your lungs," said Helen Laferriere, a nurse practitioner in St. Vincent Healthcare's internal medicine department. "So really when the air quality isn't the best, we should just stay inside."
"It depends on the amount of particulate matter in the air," said Marilyn Tapia, Riverstone Health director of health protection. "And with what we're experiencing here in Yellowstone County now, we're in yellow which is considered moderate, it would be find for health people to spend their normal amounts of time outdoors."
The DEQ website has a map of what different air quality stations are picking up around the state.