When the air is unhealthy outdoors, the warnings drive you indoors where the air should be cleaner: but often it's not.
Dr. Denitza Blagev with Intermountain Medical Center says indoor air depends on two crucial decisions:
1. Don't burn wood and/or smoke indoors.
2. Run a furnace or air cleaner with a good HEPA filter.
HEPA stands for High Efficiency Particulate Arrestance, which is measured by MERV, or Minimum Efficiency Reporting Value. When you buy a filter for your furnace or stand alone cleaner, it should have a MERV between 13 and 16.