 The Model "S", illustrated by the Sala Heater & Mantel Co. in Dallas, Texas in 1924, is an example of an early model of a convection space heater.This model consisted of three stoves and was considered to be a highly efficient radiant type of gas heater at the time.It utilizes radiant heat, and, by virtue of draft construction, supplements its power by drawing cold air through the facing, heating it, and forcing it out through the register.