I have a question concerning the classification of a natural gas fueled reheat furnace used in the steel industry. This furnace, under normal operating conditions, is basically a large (40 ft x 80 ft) box with combustion air/natural gas burners. We are in the process of installing lighting under the furnace and some believe it to be a Class I area although we have never treated it as such. One can walk under the entire furnace and it is open on all four sides. There are no gas valves or piping under the furnace but obviously we have several which feed the burners within it located above. This furnace operated at approx. 2300 degrees F so under normal operations there is certainly no gas escaping. The burners are all electrically controlled with flame detectors present so if there is a failure to ignite, the valves are then shut. We actually have two of these furnaces built very similarly however on has ventilation fans installed under it (due to heat from a less efficient design). If there are any questions please feel free to ask and yes I do have a code book just looking for a bit of clarification due to the fact that hazardous areas are something I have no experience with. Thanks in advance.