Furnaces and ovens; industrial or laboratory, including incinerators, non-electric

841710 Furnaces and ovens; non-electric, for the roasting, melting or other heat-treatment of ores, pyrites or of metals, for industrial or laboratory use 841720 Ovens; non-electric, bakery ovens, including biscuit ovens 841780 Furnaces and ovens; including incinerators, non-electric, for industrial or laboratory use, n.e.c. in heading no. 8417 841790 Furnaces and ovens; parts of non-electric furnaces and ovens (including incinerators), of industrial or laboratory use