40 CFR §98.140

1. (a)A glass manufacturing facility manufactures flat glass, container glass, pressed and blown glass, or wool fiberglass by melting a mixture of raw materials to produce molten glass and form the molten glass into sheets, containers, fibers, or other shapes. A glass manufacturing facility uses one or more continuous glass melting furnaces to produce glass.
2. (b)A glass melting furnace that is an experimental furnace or a research and development process unit is not subject to this subpart.