smokeboard

smokeboard

(ˈsməʊkˌbɔːd)
n
a board situated above a fireplace to prevent the emission of smoke into a room
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014