With multiple blazes burning, heavy wildfire smoke is blanketing parts of the United States and Canada, but that doesn’t necessarily mean you have to cancel your plans. Many experts suspect that it’s safe to hike in low to moderate levels of wildfire smoke, as long as you take a few precautions. How long can I hike in wildfire smoke before it’s unhealthy? Researchers have discovered that wildfire smoke particulates can get into all areas of the body, including the brain and bloodstream. That’s not necessarily related to wildfire smoke; ozone, a hazardous pollutant catalyzed by sunlight, worsens in hot, sunny conditions.