If the flame is produced under the hearth and then sweeps up into the
heating chamber, this is called a/an __________ furnace.
(A) Sidefired
(B) Underfired
(C) Covered
(D) Recirculating
heating chamber, this is called a/an __________ furnace.
(A) Sidefired
(B) Underfired
(C) Covered
(D) Recirculating