The owner or operator of an existing nonferrous smelter shall not permit, cause, suffer or allow particulate matter emissions to the atmosphere in excess of 0.05 grains per dry cubic foot of discharge gas, adjusted to standard conditions, from the stack or stacks serving the reverberatory furnace or any smelting furnace which replaces the reverberatory furnace.
N.M. Admin. Code § 20.2.17.109