An air quality advisory and burn ban for north central Idaho that was first put in effect last week has been extended until at least Friday. The Idaho Department of Environmental Quality’s Lewiston office announced the extension Wednesday. It covers all of Clearwater, Idaho, Latah, Lewis and Nez Perce counties, other than the Nez Perce Indian Reservation. Air quality in the region is judged “unhealthy for sensitive groups,” which includes children and the elderly, and those with heart, lung or asthma issues.