McCarraher said that when firefighters arrived, they could only see smoke because the fire itself was fragmented and hidden inside the wall. So they used a thermal imaging camera to locate any hot spots.
Such cameras allow firefighters to see clumps of heat through darkness and smoke by capturing infrared radiation.
Once the firefighters pinpointed the pockets of heat, they broke through the wall to put the flames out, McCarraher said.
Read more: http://www.milforddailynews.com/news/x1084477878/Franklin-firefighters-put-out-chimney-fire-on-Christmas-Eve#ixzz2GG2WpUEq