Various heating devices are known to the art of which the following patents are specifically known to the applications, none of which provide the specific features of the present invention: U.S. Pat. Nos. 1,990,640, Doherty; 2,492,865, Huenergardt; 2,687,469, Koci; 2,727,129, Davis, Jr.; 2,740,879, Bieling et al; 3,488,473, Sanders; 3,524,968, Walsh; 3,681,568, Schaefer; 4,096,376, Macklem.