Presto noted that the indications of good air quality doesn't apply to those in the "immediate proximity of the (Canyon) Fire" in small towns such as Westly, Newman and Patterson.
The fire raging in the hills that run through Santa Clara, San Joaquin and Stanislaus counties has charred more than 17,000 acres, officials estimate.
As a general rule, Presto says that if you can "smell smoke" that means particulate matter is entering your lungs.